Just to be extra confusing, the Cisco Small Business line of switches (SG300, SF300, etc) use a different command to display the serial number:
There is a show version command, but it does not include the serial number for whatever reason.
show ver should work for most switches
OMRCS1> (enable) sh ver
WS-C6506 Software, Version NmpSW: 6.2(2)
Copyright (c) 1995-2001 by Cisco Systems
NMP S/W compiled on May 24 2001, 19:28:46
System Bootstrap Version: 6.1(4)
Hardware Version: 2.0 Model: WS-C6506 Serial #: TBA04480798 <<<<------
PS1 Module: WS-CAC-1300W Serial #: ACP03160338
Mod Port Model Serial # Versions
In CAT4006 running older code, sh ver will not give the correct serial number. You can use "sh sprom chassis". If you have a CAT6000 running native IOS, you can use "sh idprom all"
For routers, try using "show diag". You could also use SNMP to gather serial numbers
show version shows processor board ID not the chassis number.
Some new model of routers with newer release of IOS show chassis number by using SHOW SNMP command. you can define it in router configuration by using SNMP CHASSIS
LOL.. I am noticing the time now.. It might not be helpful for the poster but might be helpful for someone who is searching for it now.. :)
Your answer just helped me also. I am thankful for the person who 14 years ago had the courage to ask the question, but what if they never received their answer? Perhaps they quit IT and are now homeless because they couldn't locate the router serial number. What if you were too late.....