Archives For Router

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)

Continue Reading…

Last year I discovered a bug in the “show crypto debug-condition” command. This bug doesn’t impact the operation of the router and is purely cosmetic. By cosmetic, I mean the output from the show command isn’t correct although the setting in the router is.

Here is what I’m talking about (compare the profile name I set in line #1 “abcdefgh” to the output you see line #11):


Router#debug crypto condition isakmp profile abcdefgh
Router#
Router#show crypto debug-condition
Crypto conditional debug currently is turned ON
IKE debug context unmatched flag: OFF
GDOI group debug context unmatched flag: OFF
IPsec debug context unmatched flag: OFF
Crypto Engine debug context unmatched flag: OFF

Isakmp Profile filters:
abcdefgh^U#G^K

Router#

Continue Reading…

identity-crisisOne 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?”

Surprisingly, a majority of candidates never get beyond physically inspecting the router to obtain the serial number.  A few give me the obvious answer of using the “show version” command and a rare handful have ever given me more than two commands that might display that information.

Yet, despite the many ways to determine the serial number of a Cisco router and the thousands of Cisco routers that I’ve managed, I finally came across this unsociable router.

Continue Reading…