Best show commands to familiarize yourself with a new network

CheesyBread

Hey everybody. I just received a job offer from within my company to be an operations support engineer. I will be in charge of 4 MPLS facing routers, 2 7613's, and a handful of switches. This is only a portion of the new position, however I would like to know what some of you senior-ish folks do to best familiarize yourself with a new network.

Obviously, I've scoured the running config, looking at the routing tables, CDP info, STP, VLAN database, and was very delighted to see that a #show interface description command had almost all of the up interfaces very well labeled. \

Anybody have any more suggestions?

ThunderPipe

I always ask for the network diagrams. Those alone will give you a (hopefully) great overview of how the network is laid out and how everything is connected. I also always ask for a tour of the facilities where all of our equipment is installed and that will help as well.

shodown

White board and GNS 3. I usually try to get the core of the site and simular configs into GNS3. There you learn how to play around with your network and get a idea of what you can and can't do and how much the PAIN of the DO's cost.

dustinmurphy

ThunderPipe wrote: »

I always ask for the network diagrams. Those alone will give you a (hopefully) great overview of how the network is laid out and how everything is connected. I also always ask for a tour of the facilities where all of our equipment is installed and that will help as well.

In a perfect world, this would be the answer. Unfortunately, some companies don't map their network. When I took over my last position (was supposedly the FIRST IT Manager for a startup, but ended up adapting a new network to an existing one), I had no network diagram. I had to make my own. I used the running configs to figure out how the network was separated, then I used an IP scanner (Angry IP scanner) to scan each network to find the available hosts (not perfect, but does a pretty good job). Then, I attempted to RDP, telnet, and ssh to each one, finding the servers and workstations. Also, if you have access to the server room, you can look around at how many different devices they have. I created my own network diagrams.

Roguetadhg

Network Diagrams? What?
Configuration files? Huh?
Documentation? Yeah right.

I found plenty of garbage though. Pretty horrified at the state I found this place. *shudders*

Relay (Frame-Relay is on my mind) on yourself to update the documentation, when in troubleshooting mode the least thing on your mind is "Are my docs correct? ...or am I seeing stupid happen?"

ptilsen

dustinmurphy wrote: »

In a perfect world, this would be the answer. Unfortunately, some companies don't map their network. When I took over my last position (was supposedly the FIRST IT Manager for a startup, but ended up adapting a new network to an existing one), I had no network diagram. I had to make my own. I used the running configs to figure out how the network was separated, then I used an IP scanner (Angry IP scanner) to scan each network to find the available hosts (not perfect, but does a pretty good job). Then, I attempted to RDP, telnet, and ssh to each one, finding the servers and workstations. Also, if you have access to the server room, you can look around at how many different devices they have. I created my own network diagrams.

Try nmap (or Zenmap, the GUI front-end). It's much more sophisticated than Angry IP. It's got a slight higher learning curve, but it will tell you what OS a given host is with pretty good accuracy. It will also tell you open ports on them, from which you can often derive OS. You can also use Spiceworks, Lansweeper, etc to get even more detailed information.

JockVSJock

I been meaning to ask this and don't want to hijack this thread.

I've also been tasked with mapping out our network, since my hotshot network admin was "too busy" to do it and has since left.

CDP is disabled on all Cisco Switches and Routers interfaces. However we only use OSPF for the routing protocol and I can use show ip ospf neighbor to get some information, however I'm not sure how to use this to my advantage to create a topology. BTW, we have some Solar Winds tools that do ping sweeps and other commands, however I can't get them to work (maybe user error, I don't know. Pings and traceroute work from the DOS command line, so I know that traffic does work).

Also the running-configs has excellent descriptions on all the interfaces, since we had to have a third party help clean this up.

So, basically in a nutshell looking for a little guidance on how to kick this off.

thanks in advance

-Jock

dustinmurphy

ptilsen wrote: »

Try nmap (or Zenmap, the GUI front-end). It's much more sophisticated than Angry IP. It's got a slight higher learning curve, but it will tell you what OS a given host is with pretty good accuracy. It will also tell you open ports on them, from which you can often derive OS. You can also use Spiceworks, Lansweeper, etc to get even more detailed information.

I'll have to check that out.... I just use Angry IP scanner because it was one of the first to come up on a Google search. I've used it for several years, and it's done what I needed... so I haven't bothered to use anything else. Thanks for the tip!

dustinmurphy

JockVSJock wrote: »

I been meaning to ask this and don't want to hijack this thread.

I've also been tasked with mapping out our network, since my hotshot network admin was "too busy" to do it and has since left.

CDP is disabled on all Cisco Switches and Routers interfaces. However we only use OSPF for the routing protocol and I can use show ip ospf neighbor to get some information, however I'm not sure how to use this to my advantage to create a topology. BTW, we have some Solar Winds tools that do ping sweeps and other commands, however I can't get them to work (maybe user error, I don't know. Pings and traceroute work from the DOS command line, so I know that traffic does work).

Also the running-configs has excellent descriptions on all the interfaces, since we had to have a third party help clean this up.

So, basically in a nutshell looking for a little guidance on how to kick this off.

thanks in advance

-Jock

In my experience, you should use a combination of different tools and techniques. Use sh run and sh interfaces to find the basics. I would even try sh ip route to find the various routes. Then, go from there... and search each avenue until you find all the devices.

Ltat42a

We used a simple little program called Friendly Pinger. You do have to create your network/topology manually. Once created, assign your IP's to the devices, it will show whether the device is up n running or not. You can also configure it to tell you (audible, visually, & email) when a device is offline, then again when it comes back up. We also used UltraVNC to remote into devices to fix simple problems, which you can add to Friendly Pinger.

Here's their website and a screen shot of a sample network.

Friendly Pinger General info


hth

Todd Burrell

For any network setup I would always recommend the SHOW CDP NEI and SH CDP NEI DET commands. These are helpful both on exams and in real life to see what it connected to what within a network. For small networks this would be very helpful.

Shanman

ptilsen wrote: »

Try nmap (or Zenmap, the GUI front-end). It's much more sophisticated than Angry IP. It's got a slight higher learning curve, but it will tell you what OS a given host is with pretty good accuracy. It will also tell you open ports on them, from which you can often derive OS. You can also use Spiceworks, Lansweeper, etc to get even more detailed information.

We use Lansweeper and Spiceworks at work. I love them both for different reasons. With Spiceworks you can create a network map and save it as a pdf file. Not only can you see the OS information but you can see other software that is installed and hardware information as well.

And of course you always have your cli commands as well. As mentioned before sh cdp nei is a great command to start with.


Good luck and congratz on the new postion!! Cheers

CheesyBread

Thanks guys.

This has been pretty hectic. The network here is insane. We have many many satellites, and an OSPF route to each satellite plus a different VRF routing table for each site connecting to those satellites. In addition each satellite has a 1.X.X.X address for the network traffic, and a 2.X.X.X for the administrative data. I've never seen such a cluster..fest. Plus there's network nodes that have a gajillion interfaces and many of them are providing routing too.

They really need a CCIE to handle this, not a CCNA I'm feeling like I'm in way over my head.

ptilsen

I think you're just overwhelmed by the amount of new input you're getting. It doesn't quite sound like it needs a CCIE, anyway.