8 Ways To Find The Serial Number of Your Cisco Router

June 27, 2014 — Leave a comment

Earlier in the week I said

One of my favorite interview questions to ask network engineering candidates is “How many different ways can you describe to determine the serial number of a Cisco router?”

…and I got to thinking: How many ways do I know how to obtain the serial number of a Cisco router?  So I began writing them down and here is what I came up with:

  1. Locate the serial number tag on the router chassis.
  2. The serial number is displayed in the banner during boot.
  3. “show version” command. (Look for “Processor board ID”)
  4. “show inventory” command. (Look for “Hw Serial#” or “SN:”)
  5. “show diag” command. (Look for “Chassis Serial Number”)
  6. “show hardware” command. (Look for “Processor board ID”)
  7. “show tech-support” command. (Displayed MANY times)
  8. “show run | s snmp-server chassis-id” command. (Must have been manually set)

I really wanted to make this “10 Ways To Find The Serial Number of Your Cisco Router” but I honestly couldn’t think of two more ways to grab the serial number of a router.  I’m certain there are probably a couple more obscure ways to do this, but I haven’t bothered scouring the IOS commands in search of alternative means of determining a serial number.  I thought there was a way to manually specify the serial number in the configuration (not utilizing the snmp-server command), but I couldn’t readily put my finger on it.

Anyway, I’ve used this question during interviews for many years and continue to do so because I believe it gives me a good insight into the individual we’re considering.  I expect the obvious answer (#1) and any combination of the rest help me to determine how familiar (hands-on experience) a candidate is with Cisco routers.  Some times when I push a candidate for more information, I receive creative responses that even while not correct reveal a person’s problem-solving mindset.  And that’s what I’m most interested in.  Plus, it’s fun to watch them squirm. 🙂

I’d love to hear from you, especially if you can share (valid) ways to determine the serial number of a Cisco router beyond what I’ve enumerated above.

Aaron Melton

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