IOS Device Troubleshooting

By stretch | Saturday, July 3, 2010 at 4:59 p.m. UTC

I've started a wiki page dedicated to explaining Troubleshooting Commands for IOS Devices in practical terms. The intent is to compile commands relevant to troubleshooting the behavior of a Cisco IOS device itself (CPU, memory, performance, etc.) and to provide an accompanying description of each.

Contributions and suggestions are welcome.

About the Author

Jeremy Stretch is a network engineer living in the Raleigh-Durham, North Carolina area. He is known for his blog and cheat sheets here at Packet Life. You can reach him by email or follow him on Twitter.

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July 4, 2010 at 12:50 a.m. UTC

Another good command is show environment.

July 4, 2010 at 4:01 a.m. UTC

I think not all cisco devices have the option "show environment", the older like 1720 don't have, and 18xx have limited information.

J (guest)
July 4, 2010 at 1:54 p.m. UTC

show stacks might be one

July 4, 2010 at 3:48 p.m. UTC

@triton: Good idea, I've added show environment.

@J: show stacks might also be a good one to include, I need to dig into it some.

July 5, 2010 at 7:14 a.m. UTC

have you'll try the command "test crash", is a undocumented cisco command can use for simulating problem. i only use this for testing in my test router.

dlots (guest)
July 5, 2010 at 1:02 p.m. UTC


That1guy15 (guest)
July 6, 2010 at 3:20 p.m. UTC

Checking ASIC utilization:

Router# show fabric utilization

or any of the show fabric commands for that matter.

This is an awesome project!

thanks a ton

July 7, 2010 at 12:10 a.m. UTC

The "show diag" command gives a fairly detailed output of hardware specs(mainboard info, onboard vpn accelerator, interface card info, etc.). Along the same lines, the "show platform" command has similar output. Benefit of "show platform" is it gives you dimm slot usage(on pre-ISRs the command is "show c", e.g. "show c1700" or "show c2600").

Also, this might not be worth mentioning but comparing numbers from "show version" and the "show memory" commands should show you how much working memory the ios image takes after loading(for whatever that's worth).

Using numbers from your output:

Show Version Cisco 3725 (R7000) processor (revision 0.1) with 124928K/6144K bytes of memory.

"Show Memory" Processor Total = 27130896 | I/O Total = 6291456

Total Installed Memory = 128MB(124928 + 6144 / 1024 = 128)

Second number in "show version" is I/O memory and is equal to the total I/O Mem in the "show memory" command: 6291456 / 1024 = 6144

IOS image should be taking up roughly around 98433K of ram(124928 - 98433 = 26495 * 1024 = 27130880). At least that's how much memory is available after the image loads.

July 8, 2010 at 3:25 a.m. UTC

I second the nod for "show diag" on a router.

Another thing I struggle with is understanding the different memory print outs on different devices and understanding how much flash, nvram, etc. a device has.

July 9, 2010 at 1:31 p.m. UTC

sh mod

sh logg

Vidya (guest)
July 23, 2010 at 10:44 p.m. UTC

"sh ipc status" is a very useful to debug IPC message drops. It shows the number of messages dropped, number of messages still queued up etc.

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