Traceroute Command

Scanning

James Broad , Andrew Bindner , in Hacking with Kali, 2014

Traceroute

Traceroute uses ICMP's Ping command to find out how many different devices are between the estimator initiating the traceroute and the target. This control works past manipulating the packets time to live value or TTL. The TTL is the number of times the packet tin can exist rebroadcast by the next host encountered on the network or hops. The command volition start with a TTL value of ane indicating the packet tin can just go as far every bit the next device betwixt the initiator and the target. The receiving device will send back an ICMP type xi, code 0 package (time exceeded), and the packet is logged. The sender increases the TTL by i and sends the adjacent series of packets. The packets will reach their expected time to live at the next hop along the network; which in turn, causes the receiving router to ship another time exceeded reply. This continues until the target is reached, and all hops along the way have been recorded, creating a listing of all devices between the initiating figurer and the target. This can exist helpful for a penetration tester when determining what devices are on a network. Windows platforms have a default TTL of 128, Linux platforms start with a TTL of 64, and Cisco networking devices have a whopPing TTL of 255.

The traceroute command in Windows is tracert . On a Linux organization, like Kali, the command is traceroute . A typical tracert on a Windows machine would look similar the following.

tracert www.google.com

Tracing route to www.google.com [74.125.227.179]

over a maximum of thirty hops:

1 1 ms <1 ms 1 ms 192.168.1.one

2 7 ms 6 ms half-dozen ms 10.10.1.2

three 7 ms 8 ms 7 ms 10.10.i.45

4 9 ms viii ms eight ms 10.10.25.45

5 9 ms 10 ms 9 ms 10.10.85.99

half-dozen 11 ms 51 ms x ms x.10.64.two

7 xi ms 10 ms x ms 10.10.5.88

8 xi ms 10 ms xi ms 216.239.46.248

9 12 ms 12 ms 12 ms 72.14.236.98

10 xviii ms xviii ms 18 ms 66.249.95.231

11 25 ms 24 ms 24 ms 216.239.48.iv

12 48 ms 46 ms 46 ms 72.14.237.213

13 50 ms 50 ms l ms 72.14.237.214

14 48 ms 48 ms 48 ms 64.233.174.137

15 47 ms 47 ms 46 ms dfw06s32-in-f19.1e100.internet [74.125.227.179]

Trace consummate.

Many of the scanning tools on Kali make utilize of protocols like TCP, UDP, and ICMP to map out target networks. The result of successful scanning stage is a list of hosts, IP addresses, operating systems, and services. Some scanning tools tin too uncover vulnerabilities and user details. These details volition profoundly enhance the exploitation phase as attacks in this stage can be amend targeted at specific hosts, technologies, or vulnerabilities.

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Domain 4: Advice and Network Security (Designing and Protecting Network Security)

Eric Conrad , ... Joshua Feldman , in CISSP Report Guide (3rd Edition), 2016

Traceroute

The traceroute command uses ICMP Time Exceeded messages to trace a network route. Equally discussed during IP, the Time to Alive field is used to avert routing loops: every time a packet passes through a router, the router decrements the TTL field. If the TTL reaches goose egg, the router drops the packet and sends an ICMP Fourth dimension Exceeded message to the original sender.

Traceroute takes advantage of this TTL characteristic in a clever way. Assume a client is iv hops away from a server: the customer'south traceroute client sends a package to the server with a TTL of 1. The router A decrements the TTL to 0, drops the bundle, and sends an ICMP Time Exceeded message to the client. Router A is now identified.

The client then sends a packet with a TTL of 2 to the server. Router A decrements the TTL to ane and passes the packet to router B. Router B decrements the TTL to 0, drops it, and sends an ICMP Fourth dimension Exceeded message to the client. Router B is now identified. This process continues until the server is reached, equally shown in Figure five.10, identifying all routers forth the road.

Figure 5.x. Traceroute

Well-nigh traceroute clients (such as UNIX and Cisco) ship UDP packets outbound. The outbound packets will exist dropped, so the protocol does not affair. The Windows tracert customer sends ICMP packets outbound; Effigy 5.eleven shows Windows tracert output for a route to www.syngress.com. Both customer types unremarkably send three packets for each hop (the iii "ms" columns in the Effigy 5.xi output).

Figure v.11. Windows tracert to www.syngress.com

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Operation Tuning

Kelly C. Bourne , in Awarding Administrators Handbook, 2014

17.2.4.two traceroute

The UNIX/Linux traceroute command (tracert on a Windows computer) identifies the route a package takes betwixt your computer and the destination computer specified in the command. Every bit a rule, you take very fiddling or no command on how a parcel gets from point A to point B. What traceroute offers across the ping command is that it lists every hop along the path between the two computers. This can aid y'all place if communications are taking besides many hops in the incorrect direction or whether certain nodes are out of commission. Figure 17.11 shows the output from a traceroute control.

Effigy 17.xi. Output of the traceroute command.

As with many troubleshooting and tuning operations, it is a expert idea to use the traceroute command when the network is operation properly. This will give y'all a good thought of what the route, the number of hops taken, and the overall times are like when conditions are normal. This will provide you with a basis for comparing so when things aren't working properly you lot'll recognize the deviation.

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Network Troubleshooting

Naomi J. Alpern , Robert J. Shimonski , in Eleventh Hour Network+, 2010

Troubleshooting the Network Layer

When troubleshooting the network layer, you'll be most concerned with routers and TCP/IP addressing.

■

Troubleshooting routers

■

Check for configuration errors or misconfiguration issues on each router

■

Bank check for a routing loop by using the tracert or traceroute command

■

Verify that a route exists to the destination network

■

Check for connectivity issues between the source and destination networks, where either a router or a network link that'southward required has failed or gone offline.

■

Troubleshooting TCP/IP addressing

■

Use the ipconfig command to verify that the IP address, subnet mask and default gateway, and other settings take been configuredcorrectly

■

Employ the route command to verify that the default gateway and other routing table entries are correct for an individual PC.

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Network Reporting and Troubleshooting

Eric Seagren , in Secure Your Network for Costless, 2007

Tracetcp

Oftentimes, the ability to know the path that network traffic is traversing is key to troubleshooting connectivity issues. In most cases you can make up one's mind this by using the traceroute utility (tracert on Windows systems). When you execute the traceroute control ICMP (Internet Control Message Protocol) is used to transmit packets to the destination with a Time to Live (TTL) value of i, and this increases for each hop. When everything goes smoothly, each hop has to reduce the TTL by ane, and when it becomes zero, the packet is dropped, and a bulletin is sent to the receiver. The trouble that often arises is that ICMP is often partially or completely filtered out by intervening routers or firewalls. In this case, yous need a fashion to reach the same thing with a protocol that has a higher chance of success.

In these cases, a TCP traceroute can be a life saver. Information technology will finer do the same affair, by manipulating the TTL values, merely it uses a TCP packet and allows a user-configurable port, which near every firewall and router will allow if it is a well-chosen port. As an instance, if yous picked a popular Spider web site and tried a trace road, you lot may get several instances of "request timed out," which indicates that the hop is non responding. In nigh cases this means that ICMP is beingness filtered by a firewall. If yous instead use a TCP-based traceroute utility and specify a destination port of eighty, you may get meliorate results. A good TCP-based traceroute utility for Windows is tracetcp from http://tracetcp.sourceforge.net/. For Linux, a very robust utility is LFT, which stands for "layer four traceroute," which can exist downloaded from http://pwhois.org/lft/.

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Configuring Cisco Routers

Dale Liu , ... Luigi DiGrande , in Cisco CCNA/CCENT Exam 640-802, 640-822, 640-816 Preparation Kit, 2009

Troubleshooting Routers

Hopefully, once you lot set up a router, you won't have any more bug with information technology. Only ordinarily, this is not the case. Sometimes, you lot volition have issues during the initial setup or later the router has been running for a while. It's important that you empathize that some of the methods can help you lot in troubleshooting common bug.

Troubleshooting Connexion Problems

Routers are basically used to connect multiple networks. Sometimes the router itself may be online just you will experience connection problems. The router may not be able to communicate with various networks or devices. Cisco offers a few User Exec level commands to troubleshoot these connexion problems.

■

PING – Y'all can use the PING control to ship test packets to a particular device. If you become a response back, you know in that location is a physical connection betwixt the ii devices. If no response is returned, this could indicate a problem with the physical connection.

■

Traceroute – The traceroute control is used to make up one's mind the path betwixt 2 connections. Often a connexion to another device volition have to go through multiple routers. The traceroute control volition return the names or IP addresses of all the routers between two devices. This also allows you to see where a packet may be misguided.

Solving Boot Issues

A less common, but more serious set of problems circumduct around booting the router. If the router does not kick properly, information technology is basically useless. It is critical that administrators understand what can be done if their router does not boot properly. Therefore, information technology's besides critical that yous understand this for the exam.

The Configuration Annals

Cisco devices incorporate what is chosen a configuration register, which is a 16-bit annals that controls router behavior. You can use this to control the terminal baud rate and control broadcast addresses. Merely, what we are near concerned with is the fact that irresolute the value of the configuration tin change how the router boots. This can exist a very useful tool in solving boot problems.

The first thing yous need to know is how to enter read-only memory (ROM) Monitor mode, which allows you to manually manipulate files and the configuration on the router without fully booting the router. You can enter ROM Monitor mode past pressing Ctrl-Break equally the router is booting, or setting the configuration to 2100. To do this, enter the following command:

If you are truly in ROM Monitor way, the IOS prompt volition appear as rommon 1> on new routers, only merely > on older routers. One time you are in ROM Monitor style, you can begin manipulating the router files and router configuration.

In that location are several other useful configuration register settings. Table 4.1 includes a listing of some of the virtually commonly used ones.

Tabular array 4.1. Cisco Configuration Annals Settings

Setting Significant
0x2101 Load IOS from ROM
0x2100 Boot to ROM Monitor fashion
0x2102 Default setting
0x2142 Ignore config in NVRAM on boot
Booting to a Different IOS Prototype

In some situations, your router may non kicking properly because of the IOS. The IOS could have become decadent for some reason. Or there may have been a problem trying to upgrade your IOS image. To help with this problem, Cisco devices will allow you to boot using a different OS. Ii common options to boot include using a different IOS image located in flash or using an IOS image on a TFTP server.

To kicking from a unlike IOS located in flash, type the post-obit in ROM Monitor mode:

Boot organisation wink ios-image-name

To kick from an IOS prototype located on a TFTP server, type the following in ROM Monitor style:

Kick system tftp ios-epitome-name tfp-server-address

Resetting the Router Password

Occasionally y'all may run into a situation where you volition take to reset the password of your router. This may be considering you take forgotten the password, or the password was changed by someone else and you practise not know the new password. As long as yous have physical access to the router, you can reset its password. It'southward very easy to do, although it does require a number of steps.

EXERCISE iv.3

Resetting Your Router Password

Here we will exist resetting your router password. Nosotros will start bypass your startup configuration so brand the changes.

1.

Connect to your router via the console cable.

ii.

Ability off your router.

3.

Power your router dorsum on.

iv.

Use Ctrl-Pause to interrupt the boot sequence. Y'all are now in ROM monitor mode.

v.

Type confreg 0x2142 at the prompt. This turns on bit 6, which will cause the NVRAM config to be ignored.

6.

Reload the router.

seven.

Enter privileged way.

8.

Enter Global Configuration mode.

9.

Copy the startup config to the running config, using

copy start run

x.

Change the router passwords.

eleven.

Type confreg 0x2102 to change the configuration register back to normal.

12.

Save the current configuration to NVRAM.

thirteen.

Reload the router.

Firmware Upgrade

The firmware running on your Cisco device is the Cisco IOS. There will come up a fourth dimension when you lot will need to upgrade this firmware. This may be necessary in club to get issues fixes or to enable new router features.

The Cisco IOS is basically a file that gets loaded at device initialization. If you want to upgrade your IOS, you but take to supplant this file with a newer file. Cisco developed the Cisco IFS (Cisco IOS File System), to help yous manage files on your router. You can utilize the Cisco IFS to copy the new IOS image to your router.

EXERCISE 4.4

Upgrade Your Router Firmware

Here nosotros will be upgrading your router firmware. This requires us to access the flash memory in your router.

one.

At the IOS prompt, type dir . This will list out the contents of your flash memory.

2.

Type copy tftp://<ipaddress>//ios-image-proper name flash:/ios-image-name

three.

Confirm the source filename. Press Enter.

iv.

Ostend the destination filename. Printing Enter.

5.

Type sh file information wink:ios-prototype-name to verify the new paradigm was copied and is runnable.

6.

Reload the router.

CONFIGURING AND IMPLEMENTING…

Deleting the current IOS image

Flash memory on your Cisco router is limited. Sometimes, to copy a new IOS to your router, y'all accept to delete the current IOS from wink. This is done using the delete command. Type delete flash:IOS-Image-Proper noun at the IOS prompt.

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ISE CLI

Andy Richter , Jeremy Wood , in Practical Deployment of Cisco Identity Services Engine (ISE), 2016

Other tools

I of the more basic merely helpful commands is "nslookup." DNS resolution is important for ISE so you tin can use this to bank check for normal A/PTR records only besides for SRV records for something like Advertizement by running "nslookup _ldap._tcp.lab.local querytype SRV." You have multiple DNS servers configured; you can also append "name-server 〈ip〉" to the end of the "nslookup" to target specific servers and so that you can pinpoint if i of them is returning incorrect data and causing random problems. The "ping" and "traceroute" commands are also useful for ensuring y'all can correctly connect between nodes.

This next one might be a bit confusing and it's the "patch" command, which is used to install patch releases onto ISE. The confusing part here is that you should not use this command from the CLI unless you have very adept reason to. The proper way to patch nodes is through the web UI, where you lot tin can upload the patch and ISE takes care of copying the lawmaking out to the nodes, installing the patch, and and then rebooting the nodes in a sequential social club then that your cluster stays in a operation state while it'due south happening. The CLI "patch" command on the other mitt only applies the patch to the one node you are currently on, a nonideal situation in most cases. If you lot are installing a patch, you probably desire it everywhere. So when will y'all utilize this command? You can use this if yous take to rebuild a node from scratch and need to bring information technology up to the same patch level equally the rest of the cluster earlier you bring together it back. Yous might also want to use this if you desire deterministic control over which nodes become a patch applied and when. The web UI will make sure that y'all never accept all of your PSNs down at the same time but if yous are a global company you will probably want to make certain that your PSNs are offline during maintenance windows for specific time zones. In that instance yous will demand to manually install patches.

Telnet is provided by the CLI likewise and while normally y'all should stay away from anything cleartext for running commands "telnet" here volition really requite us a simple way to check (some) connectivity between nodes or even to other services such as Advertizement. This image shows us some results.

You lot tin see nosotros are running the commands "telnet 〈host〉 port 〈port〉" in club to do this. In the kickoff effort we connect to port 80 which has an Apache web server listening and nosotros can see that telnet connected and basically waited for usa. Depending on the remote port you are testing information technology may act different but what's important here is the fact information technology did connect, which means we have established from our ISE node to the remote node/server the path is articulate. The next ii connections show the other possible (mutual) outcomes when testing ports with telnet. In both cases the ports tin can't connect and so we know something is wrong; in the commencement case there is nothing listening on the port used. If you were running this exam against another ISE node, you might go that mistake if the ISE services hadn't started yet. In the second attempt nosotros used iptables to replicate what you would see with a host behind a firewall/ACL; you volition notice the connexion wasn't refused but rather telnet gave upwardly connecting after a period of time.

It's normally not recommended but the commands under the "tech" commands tin be helpful for people who have *nil experience and are familiar with top/iostat/vmstat. The nice matter about these commands is that the restricted shell simply passes the output dorsum to y'all without formatting/changing it and so you lot get a more "raw" view of what's going on. The only command here you should probably avoid is "tech dumptcp" which outputs packets from a selected interface. In reality it's just running tcpdump but you can command just how many packets, if whatsoever, are captured earlier the command exits. Without any ability to filter packets you will, on anything other than a small-scale lab deployment, be overrun with packets for clients or just normal traffic and miss what you are looking for. If there is a demand to debug network communication, information technology's all-time to work with TAC and get the root patch installed so yous have direct access to tcpdump.

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Understanding the Methods and Mindset of the Attacker

Dale Liu , in Cisco Router and Switch Forensics, 2009

Nmap

Nmap is a network scanning tool that is gaining in popularity in computer defense and security. Just near everyone who performs network vulnerability assessments or plays a role in calculator/IT security has non merely heard of Nmap, but too has used it in one class or another. What used to be a scanning application used but within a control-line environment is now incorporated into other network scanning tools and has graphical front ends for ease of use.

Nmap is an open up source production, but it was developed through the efforts of Gordon "Fyodor" Lyon, who wrote the original form of this network mapper. Nmap has since revolutionized the globe of network security and computer defense. One of its major features is its ability to exist customized for a variety of purposes and tasks. For instance, it tin browse in i configuration 1 moment, and and then, with a few simple keystrokes, you can customize it to work in an entirely unlike way. Although Nmap has a ton of features, it has a bit of a learning curve for people who accept had piddling experience with network scanning and reconnaissance. The original version of Nmap was command-line interface (CLI) driven, and then you lot had to type in the commands, switches, and flags to start a scanning event. But Nmap was ported out to other platforms, including Microsoft Windows, and a GUI version became available.

If CLI entry of commands isn't for you, you have a few options. If y'all are working on a Windows PC, Nmap is available with a GUI front end that requires that you simply fill in some blanks and bank check some options to prepare up the application.

If y'all are running a Linux system, you may want to look into the NmapFE or Zenmap package (I am referring to .rpm packages for Fedora Linux fans and .deb packages for those using Knoppix or Ubuntu/Kubuntu). It's the aforementioned point-and-click procedure every bit the Windows version, just within the Linux environment.

As merely noted, Nmap is capable of performing several tricks, but it takes some endeavor to learn how to use all of its features. Some of its features include a choice of scanning method, timing options, name resolution, spoofing and decoy functions, and diverse output methods. Effigy vii.ii shows several runs of Nmap on a range of network addresses.

Figure 7.2. Nmap Scan on a Network Subnet

Earlier we talk over some of the scanning mode selections that you can make with Nmap, you should make sure you empathise basic networking fundamentals such as TCP flags, connection versus connectionless protocols, and other technical terms. You may desire to consult the document on Cisco'south Web site at http://world wide web.cisco.com/en/U.s./docs/internetworking/technology/handbook/Internet-Protocols.html for a refresher. I also recommend y'all expect at this IT Security Basics article that is maintained in the SANS Reading Room. It covers good security data especially on the subject of DOS and MitM attacks: http://www.sans.org/reading_room/whitepapers/basics/information_security_primer_443?show=443.php&true cat=basics.

Nmap tin can scan both hosts and networks in a diverseness of ways. You can configure certain controls, such as speed and aggressiveness, via CLI or through a front. For instance, Nmap incorporates six unlike timing templates. You refer to the templates using the –T switch, and they work to govern the period of Nmap packets down range to their target. The range goes from five minutes per probe packet (T0) to five milliseconds (T5) per probe parcel, so you take a great deal of control over how quickly a browse is kicked off and how much noise it makes to the intrusion detection system/intrusion prevention systems (IDS/IPS) keeping watch over the network. This is to let someone who wants to run his scan slowly and so that he can avoid detection. This flexibility sets them apart from the crazies amongst us who similar to saturate the network with our Nmap probes. Scanning the network also rapidly as well makes those crazies liable to be detected much quicker as a direct outcome.

Nmap is also capable of scanning hosts in a number of ways to run across sure requirements and circumstances. Nmap can scan its target hosts using Manual Control Protocol (TCP) packets, User Datagram Protocol (UDP) packets, IP packets, and other configurations. When it comes to TCP probe packets, Nmap can course the packets with specific TCP flags set, such as the SYN, RST, ACK, FIN, URG, and PSH, in whatever configuration suits your fancy. The reason for this is that some firewalls or admission control lists (ACLs) are prepare to audit the contents of the flags and make their decision to pass, drop, or pass up based on certain criteria. One particular Nmap scan configuration is called XMAS because the FIN, PSH, and URG flags are set (brightly lit, like a Christmas tree), and this may or may not escape parcel inspection. Some IDSs will central in on this as they may take a configured detection signature that triggers on seeing this combination; this is called an NMAP XMAS-Tree scan. But this, besides, can be avoided by setting a flag override.

Once when I was at a former piece of work site, I was informed (and disappointed to learn) that the network security staff decided to limit the remainder of the staff's ability to troubleshoot network connectivity by blocking Internet Command Message Protocol (ICMP) ping traffic in and out of the routers throughout the campus network. Then, ane day the traceroutes would no longer work every bit the policy was enforced. Nonetheless, on a particularly hot twenty-four hours, I discovered that when I second-naturedly typed in a traceroute control on an Apple Mac running Bone ten, I found that it was working across the subnets and all over the network. As information technology turns out, the security admin had disregarded the fact that Windows systems use UDP packets for their tracert command, only Os 10 pushes out ICMP packets, and they were being overlooked. My colleagues and I became highly interested in what else we could pass.

The moral of this story is to ensure that your policy works as expected in all forms, from soup to nuts. If you fail to completely battle-test your new ACL or your firewall rule, someone like your dominate is going ruin your day and you may take some difficult questions to respond in the result of a horrendous compromise.

Some other of import characteristic of Nmap is its ability to scan ports and tell y'all all sorts of things nearly the host that maintains them. Nmap can not only browse any of the 65,536 ports on a host, but it can also derive certain data from them. Call back that ports are usually in ane of several states: open up (accepting connections), airtight (every bit in airtight for business), and filtered (which may be some other way of maxim "firewalled"). In some cases, a port may exist reported as unfiltered, meaning that Nmap cannot determine whether information technology is filtered, and is not completely sure it is open to make connections. Not only tin Nmap report on this, but information technology can hands go further and determine what type of operating system controls the network services on the target hosts. Different operating systems have different responses to certain network events, and past closely examining the subtle timing differences and responses returned to its probes, an Nmap procedure tin brand a decent, intelligent determination of the operating system it is probing. Nmap can get fifty-fifty further and perform service detection on ports. How many times have you heard someone say that he was going to hide network service by putting it on a non-standard, not-so-well-known port in an effort the reduce attacks to his system? Well, Nmap is capable of detecting whether someone has tried this past setting a Secure Shell (SSH) server to run on port 53 as it knows the differences between SSH and domain name organisation (DNS) servers.

Tons of techs I run into are thrilled with Nmap's Bone detection feature (available by invoking the –O switch). Well, Nmap as well offers a service fingerprinting feature (available past invoking the –sV switch). This can help to confirm the Bone detection results besides as requite you insight into the precise services that are running on the system.

Nmap is besides known for its output and reporting features. The software can requite you its scan results in a variety of ways. As you saw in Figure 7.2, each port condition appears on a line past itself, and unremarkably that is okay for a visual display. But when y'all are scanning dozens to thousands of hosts, you lot will non want to look at this data line by line when yous can run the results through a text-searching tool to categorize the results. Toward that cease, Nmap is able to too dump its results to an XML-formatted file, or to a file you tin can search using a grep command (or any you similar that is capable of running regular expression searches/filtering). Nmap too offers the selection of putting the results in all three formats if you want, and all yous accept to do is provide a base filename in the command before you kick off the scan.

Notes from the Underground…

So, Do Y'all Really Call up Y'all Know Who Is Scanning You?

Are you interested in knowing how adept penetration testers keep their addresses hidden for as long as possible? Information technology's a thing of hiding amidst the other IP addresses which are present, and spoofing an IP address. Ii cool ways that you can obfuscate your IP address as the source of scanning action involve using the decoys office and spoofing your Media Access Control (MAC) address.

Hither we take chosen to designate a few extra decoys along with our browse to brand the scans appear as though they are coming from a number of systems, rather than simply ours. (Call up the age-old rule of safety in numbers!)

Here is an example of this technique sending ACK flags to port lxxx at Captain Insaneo-speed:

#nmap –n –PA –p 80 –T5 –D 10.one.1.one,ten.ane.2.1,66.1.ii.half dozen,ME,202.3.192.one <target>

As far as MAC address spoofing is concerned, today it is like shooting fish in a barrel to spoof the source MAC address of the interface Nmap is using, and you don't even have to expect information technology up. Say, for instance, that you visit an fine art studio with an Alienware system equally your vulnerability cess calculator, and all your targets are Macintosh systems. If you run an Nmap scan without making a change to obscure your organisation's identity, your arrangement is going to stick out like a sore thumb. So, you conjure up some "lucky charms" and use a item MAC accost vendor—and throw the security officeholder for a loop as he goes effectually looking for an HP Compaq system. Here is the Nmap command you would pass in this case:

#nmap –n –PA –p 870 –T5 –spoof-mac HP <target>

If you wanted him to think that a Linksys router was involved, try this:

#nmap –n –PA –p 870 –T5 –spoof-mac Linksys <target>

Adept times!

Although we talked about only a scattering of features, Nmap has numerous others that we don't have the infinite to cover. Suffice it to say that Nmap has made a huge bear upon on calculator security and arrangement administration and most likely will continue to do then as it continues to be developed through open source participation from around the globe.

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UNIX Tools

Kelly C. Bourne , in Awarding Administrators Handbook, 2014

24.10 Connectivity

More than likely your awarding server doesn't exist in a vacuum. The application might consist of multiple servers, e.g., a spider web server, a written report server, etc. The application might be in a load-balanced environs. It might utilize a cluster to ameliorate either functioning or availability. The database very probable resides on a dissever, dedicated server.

If any of the higher up situations exist in your environment, then you're going to be dealing with multiple servers. Multiple servers means that you'll take to sympathize how to communications between those servers occurs. The tools or commands listed in this section can provide insight into communications between servers or between your server and the larger earth.

As an Application Ambassador perhaps your virtually troublesome bug will be dealing with potential connectivity issues. When hunting down connectivity problems it's helpful to have a checklist of things to cheque and always run through them in order. Subsequently a while you'll go a feel for what's causing the issue this fourth dimension. Some examples of typical connectivity-related problems include the following:

•

Is the awarding server experiencing problems connecting to the database server?

•

If the application is running on multiple servers, due east.one thousand., an application server and a reports server, are they able to connect to each other?

•

Are users having problems connecting to the application server?

•

Are users able to connect to the system's network?

•

Can users access the organisation'south network from a remote location?

•

Are functioning problems experienced by users being acquired by the application, the database, the network, or something else?

To troubleshoot problems similar the ones listed above you demand to know what tools are available on your server. Every organization's environment is different, but the tools that are described in the following sections are probably available on your UNIX server. The sections are organized from the simplest check first and the most complicated checks last.

24.10.1 ping

The ping command was described in Chapter 23. Information technology works essentially the same nether Windows and UNIX. Enter "ping" and another computer's name or IP address. The format of both ping commands is shown hither. Ping will determine if the destination is reachable. If ping continues to display output lines you can press Ctrl-C to impale it:

ping computer-name

ping IP-address

If you get an error bulletin saying the ping control is not found then try entering ping as follows:

/usr/sbin/ping estimator-name

There are two potential shortcomings to using the ping control. The start is that if y'all enter the proper noun of the remote calculator it'due south possible that your DNS (Domain Name Organisation) server is translating the server name you lot entered to the incorrect IP accost. If an inaccurate IP address is being provided, this could be the source of your problem. To determine whether or not this might be the problem y'all should compare the IP address returned by a "ping computer-name" command with your documentation that identifies the IP address of the remote computer. If the IP address returned by the ping-by-proper name doesn't match your records, so a problem exists in the DNS area. Contact your network team and work with them while they resolve it.

You should besides execute a ping command and specify the IP address of the remote computer. This volition help you determine whether the remote figurer tin can be accessed if an accurate IP address is being used.

The previous advice assumes that yous take a "landscape" certificate or other documentation that shows the name and right IP address for all of the organization's computers. If this documentation doesn't exist, so now would exist a very good time to create information technology.

The second potential problem with a ping command is that some servers have been configured to ignore ping commands. This is done as a security measure to help protect them from DOS (deprival of service) attacks. If you lot get the result "Asking Timed Out" every fourth dimension you ping a particular server, so this probably means it has been prepare to ignore ping commands.

24.10.2 Database connectivity

If your connectivity trouble appears to be related to the database, then you should meet if the database server tin can exist accessed from the awarding server. At that place may be a tool on the application server that enables you to initiate a database session. For example, if the database beingness used is Oracle, and so SQL*Plus has likely been loaded onto the application server. Open a SQL*Plus session with the database using a command like the following:

sqlplus username/[email protected]

If the session established, it proves that connectivity with the database server exists. If the SQL*Plus command fails, so a trouble exists. The adjacent step would be to work with the DBA team to ostend that the database engine is running. If it is, so you might demand to piece of work with the network team to verify that the awarding server can communicate with the database server.

24.10.3 Traceroute

If the ping-past-proper noun and the ping-by-IP were unsuccessful, then you need to find out where along the path betwixt your server and the destination it failed. You need to know if your computer is able to communicate with the Internet or other networks. Your organization has a device chosen a gateway router that acts as a gateway between your network and all other networks. Run the "traceroute" control to determine whether your communication attempts are getting out the door so to speak. If the results bespeak that your traceroute attempt didn't make it past your gateway router, then you demand to contact your organization'due south network team to resolve the problem.

traceroute, similar ping, confirms whether or non connectivity to the destination calculator can be established. The output from traceroute indicates how many servers or hops it takes a parcel to get from your server to the destination computer. The format of the traceroute command is:

traceroute destination

where destination can be either a name or an IP accost.

This command tin exist very informative if communications with some other computer are extremely slow. It can tell you lot either that the packets are taking an excessive number of hops taken along the path or that a specific computer in the path is taking longer than expected to communicate. If either of these is the case these, the problem isn't with your server.

24.10.4 tnsping

tnsping is a utility provided by Oracle that determines if connectivity to the Oracle database server can be established. If your awarding uses an Oracle database, then you lot tin can use tnsping to make up one's mind if the application server can communicate with the Oracle database server. The format of the command is:

tnsping service-name

If you don't know the value of the service name you tin find information technology in the tnsnames.ora file within the Oracle Client software subdirectory.

24.x.5 netstat

netstat displays the following network communications related information:

•

Agile ports—running netstat with the—an option displays a list of all active ports. This means a listing of incoming and outgoing network connections that are currently open on the server. Information technology likewise lists the process that opened each port, whether the port is open up for input or output and what protocol is being used.

•

Routing tables—the routing table holds the list of computers that can be directly communicated with. It might be a surprise to yous, but your server isn't enlightened of every server on the Cyberspace. It is aware of a few other computers which are aware of a few more computers which are aware of still more computers, etc. To view merely routing table data include the –r option when calling netstat.

•

Statistics by protocol tin can be obtained by running netstat with the –s option displays a listing of statistics for each of the protocols (tcp, udp, ip, icmp, igmp) that are supported. Some of the stats that are displayed are: packets sent, packets received, connection requests, connection accepts, connections established, and timeouts.

24.x.6 ruptime

ruptime, remote uptime, shows the status of all machines on the network. Information technology also provides information on how long each calculator has been upward and what its contempo load level is. The formation of ruptime is as follows:

ruptime

24.ten.7 rwho

rwho, remote who, lists who is logged onto all machines in network. Be aware that rwho isn't bachelor on all networks due to security concerns. If you need to know who is logged into another computer and "rwho" doesn't work, then yous'll have to remote to that machine and run "who" on it. The format of this command is:

rwho

24.10.8 nslookup

If your users or application is no longer able to connect to a server, the problem could be that the local name server has out of date or otherwise inaccurate information. The nslookup command allows you to query the Domain Proper noun Organization (DNS) to gather information on domain names it contains. Using it you can larn the name and IP accost of the name server that is being used. You can likewise obtain the IP addresses of machines that the proper name server is maintaining information on.

Figure 24.8 shows the results of an nslookup call to become the details on server "dr005." The nslookup command has other available parameters which tin be seen on the man page for it.

Effigy 24.8. nslookup command.

24.10.ix Firewall problems

It's possible that your organization'southward firewall is causing the connectivity bug. It's not uncommon for a modify in a firewall's configuration to cause problems connecting to a server that was working just fine yesterday. Depending on your level of expertise yous could investigate this yourself or contact the arrangement'southward team that administers the firewall. A word of warning is definitely in order here: exist very careful not to cause bug or brand unapproved changes of the firewall. Doing so could crusade extremely serious problems for y'all, your users, other applications, and their users.

If you're cognition about the organization's firewall, you might consider checking the firewall configuration or its logs to see if there are any clues well-nigh the problem. Two commands that might provide some insight are:

iptables –n –L Lists all rules configured in the firewall. If you're non familiar with firewall rules, then the output from this command will probably be undecipherable to you.
tail –f /var/log/letters Repeatedly lists the 10 most recently added entries in the log files located in directory /var/log/messages.

24.10.10 Network analysis tools

At that place are a number of network analysis tools that tin be acquired to provide detailed data on the communications between your server and other machines. Providing an in-depth description of any of them is beyond the scope of this book, but a brief description of some tools that are available is provided.

24.10.10.i tcpdump

tcpdump is a packet analyzer that is launched from the control line. It can exist used to analyze network traffic past intercepting and displaying packets that are being created or received by the calculator information technology'southward running on. Information technology runs on Linux and near UNIX-type operating systems.

24.ten.10.2 Wireshark

Wireshark is an open source tool that is used for troubleshooting network bug. Information technology runs on Linux, Windows, and many UNIX-like operating systems. Yous can employ Wireshark to capture all packets on the network, just need to be careful that the book of traffic being captured doesn't become overwhelming. The GUI (graphical user interface) in Wireshark makes it relatively piece of cake to capture only the specific traffic that you're interested in.

24.10.10.iii Cheops

Cheops is an open source package that provides numerous network-related utilities. Using it y'all can locate, diagnose, and manage network resources. It can identify the operating systems of all hosts on the network. It provides a mapping of your network and if it'due south especially large y'all can break the overall map down into multiple views. A port scanner documents what tcp ports are being used.

24.x.11 Connectivity tools

In that location are a number of connectivity-related tools available in UNIX. They are described in the following sections. Application Administrators should take at least a working cognition of connectivity tools.

24.ten.xi.1 Telnet

Telnet is a utility that enables you lot to remotely connect to another computer and open a terminal session on it. Employ of telnet has diminished significantly because it isn't a secure communication method. If you want to log onto another computer using telnet the format is:

telnet remote_computer.domain.org

Yous will exist prompted for an ID and password to complete the connexion process. If the computer is on the same network as the calculator y'all are logged into, then you tin omit the ".domain.org" from the command.

24.10.11.2 rsh

Rrsh (remote beat) is another method of remotely connecting to another computer and running a terminal session on it. To apply rsh to open up a session on a remote computer, you must have an account on that figurer. When the connectedness is established, you'll be prompted to enter your countersign. The format for using rsh is:

rsh remote_computer.domain.org

One variation of rsh is that it can be used to execute just a single control on the remote computer instead of opening a terminal session. The format for using rsh in this style is:

rsh –fifty username remote_computer.domain.org command

24.10.11.3 ssh

ssh (secure shell) is a more than secure way to log onto a remote organization. ssh offers similar functionality to rsh merely more deeply. Communicates passed betwixt computers during an ssh session are encrypted, so they are much better protected than either telnet or rsh. The format of the ssh command to initiate a remote concluding session is:

ssh remote_computer.domain.org

You lot will be prompted for the password before the remote session is established.

24.x.11.four PuTTY

PuTTY is an open source utility that allows you to connect with remote computers. Although it was originally written for Windows it has been ported to a number of UNIX platforms. PuTTY was described in detail in Section 23.5.4 of Chapter 23.

24.10.xi.5 ftp

ftp, file transfer protocol, is a UNIX application that is used to transfer files betwixt machines over a network. At that place are numerous GUI implementations of ftp, but most UNIX systems back up the command line version of this tool. To initiate an ftp session enter the following command:

ftp remote_computer.domain.org

Y'all will be prompted for your username and password. Once your ftp session has been established, you lot tin utilise whatever of the following basic instructions to transfer files to or from the remote calculator:

•

cd—change the working directory on the remote computer

•

lcd—change the working directory on your local reckoner

•

mkdir—make a directory on the remote computer

•

ls—list files in the working directory on the remote computer

•

bin—sets the mode then file will be transferred in binary mode

•

asc—sets the mode so files will be transferred in ASCII, i.eastward., characters, mode

•

put—moves a file from the local computer to the remote computer

•

go—retrieves a file from the remote estimator to the local figurer

•

assist—displays a list of available commands and their parameters

•

quit—get out out of the ftp session

24.10.11.vi rcp

rcp, remote copy, is a UNIX command that allows y'all to transfer one or more files to or from a remote computer. In order to motility files to or from another computer, you lot must already have an agile account on the remote machine.

The format of a basic rcp command to copy a file to a remote estimator is:

rcp example.txt [email protected]_computer.domain.org:

The command to copy a file from a remote computer to your local computer is:

rcp [email protected]_computer.domain.org:example.txt

24.ten.eleven.7 scp

scp, secure copy, has similar syntax and functionality as rcp, but is more secure. SCP encrypts the contents of the file earlier transferring it. If someone is capturing and examining the packets in your file transfer they wouldn't exist able to read them.

The format of a basic scp command to copy a file to a remote computer is:

scp example.txt [e-mail protected]_computer.domain.org:

The command to copy a file from a remote figurer to your local estimator is:

scp [email protected]_computer.domain.org:instance.txt

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Troubleshooting the Juniper Firewall

Brad Woodberg , ... Ralph Bonnell , in Configuring Juniper Networks NetScreen & SSG Firewalls, 2007

Troubleshooting Tools

The Juniper firewall has several troubleshooting tools built in to it. This section covers these tools in item. Each has a specific purpose and should encompass any troubleshooting needs yous have.

Tools & Traps…

Secure Troubleshooting

One thing you want to make certain of when troubleshooting your firewall is that y'all don't compromise your security during the troubleshooting process. If you lot're using HTTP (Hypertext Transfer Protocol) or Telnet to access your firewall, someone may be able to sniff your packets while you're working to solve the problems.

The WebUI can be encrypted with SSL (Secure Sockets Layer) or tunneled through a VPN. Information technology is recommended that this connection be secured at all times. The certificate can be self-signed by the Juniper firewall, so no certificate has to exist purchased.

The command-line interface can be encrypted by using SSH (Secure Trounce) to log in to your firewall. Telnet should be disabled so it cannot be used by anyone. If Telnet access is required for some reason, exist sure to encrypt the packets using a VPN tunnel. Serial console access requires physical access to the firewall. You can disable all CLI access if you wish and require serial access to manage the box, but this mensurate might be a chip extreme.

Ping

Ping is probably the most well-known network troubleshooting utility in existence. The ping command is used to test for network connectivity. Every network operating organisation has a version of it preinstalled. It was written in December, 1983 by Mike Muuss for BSD Unix. The BSD Unix network stack has been ported to many operating systems, including every version of Microsoft Windows. Although the name was originally derived from a sonar analogy, it is now referred to as an acronym for Package InterNet Groper.

The functionality is simple: send an ICMP (Internet Command Bulletin Protocol) echo-request and look for an ICMP echo-reply. The code shown in Figure thirteen.1 is an example of sending a ping to IP accost 192.168.0.i, and getting four replies in render. This is a connectivity check from a Windows machine to a router.

Effigy 13.1. The ping Command in Windows

Past default, the NetScreen device volition send v ICMP echo requests of 100 bytes each with a ii-second timeout. Avant-garde settings can as well be included on the control line:

You may also set all of the options manually by entering only the command ping and pressing Enter. At this point, you lot will be prompted for each one of the options to build the control you wish to execute, specifying target IP, the number of requests, the datagram size, so on.

Figure 13.2 shows an instance of using the ping control in ScreenOS v.

Figure xiii.2. The ping Command in ScreenOS-5

Proceed in heed that the results of the ping control may not always exist authentic. Some network traffic does not pass ping traffic and could peradventure change the results of the command.

You can too ping from a specific interface with the ping command ping <ipaddress> from <interfacename> (see Figure 13.iii)

Figure thirteen.3. Pinging from a Specific Interface
traceroute

The traceroute control is useful in troubleshooting multihop routing. traceroute uses the TTL (Time to Alive) field of the IP protocol to get an ICMP TIME_EXCEEDED response from each gateway the package goes through to reach the destination. Figure 13.4 shows an case of traceroute in ScreenOS.

Figure 13.four. traceroute in ScreenOS

traceroute results should also be taken with a grain of table salt. Since traceroute uses TTL fields in the packets, whatever devices that do not respond to that field will non return valid data.

Get Session

The go session control volition show all current established sessions going through the Juniper firewall. If an entry exists in the session table, the connection has passed through the routing tabular array and the policy successfully.

Each session entry has iii lines of information. The first line contains the policy rule number, which can exist viewed past the get policy control. The fourth dimension entry shows idle fourth dimension and resets every time traffic goes through the firewall. Effigy thirteen.5 illustrates these points.

Effigy 13.v. Get Session in ScreenOS

The output from the get session control tin seem a fleck overwhelming at outset, but it isn't really that bad once you break it down. First, the command specifies how many sessions are currently allocated (in the preceding case, information technology is 64 with a maximum number of 128064). This command too specifies how many sessions failed to exist allocated (both regular and DI sessions) and how many multicast sessions are allocated. Information technology also provides statistics for the memory and sessions pools. The next part of the command that you really should be concerned with is the information about the source IP accost, source port, traffic direction, destination address, and destination port. The first entry in Figure 13.5 is: 218.172.211.178/18772->123.49.20.57/1024. This stands for a source address of 218.172.211.178, with a source port of 18772 going outbound to destination 123.49.20.57 port 1024. Information technology will be using route 0, which y'all can verify with the get route control and compare that confronting the route ID value in the output. Traffic with the <- symbol designates the entering (return) traffic. The return traffic may also show the NAT'd value of the packet, and the subsequent route which may exist taken to reach the destination. You can likewise run into which policy (in this case 320000) is being matched for this session.

Go Policy

The get policy control displays the electric current NetScreen policy. This control is useful as a reference to meet which policy ID is assigned to each rule. Pay attention to the From and To fields. These point which zones each policy crosses, as shown in Effigy 13.6.

Figure 13.6. get policy in ScreenOS

Get Route

The become route command shows the current NetScreen routing table. There is a dissever routing table for each virtual router. In the example in Figure thirteen.7, there are no routes for the untrust-vr, which is the default configuration. Brand sure you differentiate which routes are static and which are added by a routing protocol.

Figure 13.7. get route in ScreenOS

Remember that the * next to a route designates that information technology is the active route in the routing table, and the ID is the value that is too referenced in other troubleshooting commands such every bit the go session command. This output shows you that route 12 is active over the same route (different next hop) route 13. They are both Static routes with a preference of 20, and a metric of 1. It is not immediately clear in this case why route 12 is valued higher than xiii, merely the reason could be because ethernet0/one is physically downwards.

Go Interface

The become interface command shows detailed interface statistics. This command (shown in Figure 13.8) is useful to run across which zone an interface is in and which hardware MAC (Media Access Control) address is assigned to each interface. You can besides run into the IP address, VLAN, and what land the interface is currently in (U for Up, D for Downwards.)

Effigy 13.viii. become interface in ScreenOS

Go ARP

The ARP (Address Resolution Protocol) table of the Juniper firewall tin be viewed by using the get arp command. This can be useful when troubleshooting OSI layer 1 and layer 2 issues. Figure 13.9 shows the ARP table of the Juniper firewall.

Effigy 13.9. go arp in ScreenOS

We can meet in this case that the MAC address for 218.172.211.177 is invalid (000000000000.) It also specifies what interface this will try to larn the MAC address on, which will be whatever interface has an IP address in the same subnet as the IP accost that yous are ARPing for. This can be very useful to troubleshoot layer 2 issues, peculiarly when devices are continued directly to your firewall.

TIP

Delight call back that if y'all are replacing ane network gateway device with another (such equally the SSG), the MAC address will modify because at that place will be a new hardware interface in place of the erstwhile ane (assuming yous are keeping the aforementioned IP address). This will mean that other devices may non recognize this new MAC address until either their ARP cache times out (often ten minutes on most systems), or you can manually articulate it, such equally issuing the clear arp on the Juniper firewall, or arp –d on Windows.

Get System

The go system control gives yous several important pieces of information. Apply this command to go an overview of your firewall and the setting for each interface. On an unknown firewall, this should be the first command yous utilize.

▪

Serial Number This can be used to reset the device to the factory defaults. Use the serial number as the username and password when logging in on the series interface. Be enlightened that this will also wipe out whatever configuration changes you accept fabricated. The serial number is used to generate the license keys for your device besides.

▪

Software Version The software version of the ScreenOS device in running memory.

▪

Engagement and Time Returns the date and time on the NetScreen device.

▪

Total Device Resets Tracks the total number of asset recovery resets. This number counts the number of times the system has been reset to the factory defaults.

▪

User Proper name The username of the electric current user.

Debug

The debug utility in ScreenOS is a powerful troubleshooting tool that allows yous to rails sessions going through the Juniper firewall. The firewall has a memory buffer set aside for the debug organisation, and packets can be captured in this retentiveness for inspection. The post-obit outlines various uses of the debug organisation:

Step i.

Set any filters necessary for the debug. This is optional, but it might help consolidate the results. Optionally, you lot might also want to clear the buffer of old debugs so that you get a meliorate snapshot.

Step ii.

Effect the Debug Command.

Step 3.

Issue the get db str command to get the output stored in the memory buffer from the debug.

Step 4.

Cease the debug with the undebug all command which volition halt whatever debugs. Alternatively you can continue issuing the get db str command to go on getting output from the debug.

Step 5.

Articulate the memory buffer with the clear db control.

Alarm

You must be mindful that issuing debug commands can increase the load on the firewall. Althought it is not as crippling as debugs on other platforms (historically,) it can cause issues if you are not careful. It is best to use flow filters, and plow the debugs off as shortly as possible.

Flow Filters

A filter can likewise exist put into place to limit what traffic gets sent to the debug buffer. The command fix ffilter allows y'all to select the blazon of traffic to collect. The following filters are available:

▪

dst-ip Destination IP address

▪

dst-port Destination port

▪

ip-proto Internet protocol number

▪

src-ip Source IP accost

▪

src-port Source port

If multiple filters are specified in the set ffilter command, the filter volition simply collect traffic that matches all of the filters specified. The set ffilter command can be executed multiple times, and traffic will be collected if it matches any of the filters. For case, to filter all tcp traffic from 192.168.0.1 to 10.one.1.1, issue the following command:

SSG550-> set ffilter src-ip 192.168.0.ane dst-ip x.1.ane.1 ip-proto half-dozen

To view current filters, apply the go ffilter command. Each filter in place has an ID number to identify it. To remove a filter, use the unset ffilter command, followed by the ID number of the filter to be deleted.

Snoop

Snoop is a full packet sniffer. The output of snoop goes into the aforementioned memory buffer that debug sends to. The biggest difference betwixt debug and snoop is that snoop can dump the bodily contents of the packets to the memory buffer. snoop output is more than difficult to read than debug output and is typically used when the contents of the packets need to be analyzed. The post-obit are the commands for using snoop:

▪

snoop Starts the snoop capture.

▪

snoop info Displays current snoop status.

▪

snoop detail Enables full packet logging. This logs the total contents of the packets.

▪

snoop off Turns off the snoop capture.

▪

snoop filter Allows you to filter what gets captured. Employs syntax similar to that used for debug filtering.

▪

clear db Clears the debug memory buffer.

▪

go dbuf stream Displays the output for assay.

Firewall Session Analyzer (FSA)

Juniper has created a new Spider web-based tool chosen Firewall Session Analyzer (FSA) to assistance make sense of the torrent of data that tin come up from running a get session command. As discussed before, this command shows all current established sessions going through the NetScreen device, and this can seem a little daunting when viewed in the console.

Afterwards uploading a log of the get session control output to the FSA (located at http://tools.juniper.internet/fsa/), it volition generate the following seven reports.

▪

Rank based on destination IP address

▪

Rank based on destination port

▪

Rank based on source IP address

▪

Rank based on source port

▪

Rank based on protocol

▪

Rank based on Virtual Organisation Device (VSD)

▪

Rank based on source IP with protocol and destination port information

In club to use the tool, you need to log the command output to a file on a TFTP server by using the following command.

SSG550-> get session > tftp <server ip> <filename>

You may besides choose to capture the screen output to a file and upload information technology to the analyzer in the aforementioned manner as the file stored on the TFTP server. Once you accept the log file, generating the FSA reports is simple.

i.

Go to http://tools.juniper.net/fsa/ using your Web browser.

ii.

Browse to your get session .log or .txt file, first making sure the file does not exceed 10MB.

iii.

Choose the version of ScreenOS the file was captured from (ScreenOS v4 or v5).

4.

Click Submit. After several seconds, your results will be viewable in a new screen.

The top 10 results for each of the seven previous reports will be viewable on i page (come across Effigy 13.10), at which indicate you can download each complete written report as an individual csv file past selecting the link for the report you desire. This information will be bachelor for you to view for 1 hr following the execution of the analyzer. After one hour, the data candy by the tool, and the corresponding reports, will exist deleted from the Juniper site for security reasons.

Effigy 13.10. Firewall Session Analyzer

Putting It All Together

When troubleshooting the Juniper firewall, use whatever of the previous commands necessary to resolve the issue. When a bundle arrives at an interface of the firewall, the post-obit things happen.

i.

The package goes through a "sanity check" to brand sure it isn't decadent.

2.

A session lookup is performed. If the parcel is role of an existing session, it follows the rest of the packets in the same session.

iii.

The parcel is routed, based on the routing table and zones.

iv.

The packet is checked against the firewall policy.

5.

The ARP cache is referenced.

6.

A session is created if one does not be, and the packet is forwarded.

Observe that the session is not created until the packet passes through the routing tabular array and the firewall policy.

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