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?”
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.
Here are the results from a “show version” command on a Cisco C881-series router. You can actually see the serial number (FTX18138205) is displayed multiple times in this output. This is the way it should look:
Router#show version Cisco IOS Software, C800 Software (C800-UNIVERSALK9-M), Version 15.4(1)T1, RELEASE SOFTWARE (fc2) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2014 by Cisco Systems, Inc. Compiled Wed 12-Feb-14 06:45 by prod_rel_team ROM: System Bootstrap, Version 15.4(1r)T, RELEASE SOFTWARE (fc1) Router uptime is 2 minutes System returned to ROM by reload at 11:38:09 UTC Fri Jun 20 2014 System image file is "flash:c800-universalk9-mz.SPA.154-1.T1.bin" Last reload type: Normal Reload Last reload reason: Reload Command This product contains cryptographic features and is subject to United States and local country laws governing import, export, transfer and use. Delivery of Cisco cryptographic products does not imply third-party authority to import, export, distribute or use encryption. Importers, exporters, distributors and users are responsible for compliance with U.S. and local country laws. By using this product you agree to comply with applicable laws and regulations. If you are unable to comply with U.S. and local laws, return this product immediately. A summary of U.S. laws governing Cisco cryptographic products may be found at: http://www.cisco.com/wwl/export/crypto/tool/stqrg.html If you require further assistance please contact us by sending email to email@example.com. Cisco C881-K9 (revision 1.0) with 988236K/60339K bytes of memory. Processor board ID FTX18138205 5 FastEthernet interfaces 1 Virtual Private Network (VPN) Module DRAM configuration is 32 bits wide 255K bytes of non-volatile configuration memory. 250880K bytes of ATA System CompactFlash (Read/Write) License Info: License UDI: ------------------------------------------------- Device# PID SN ------------------------------------------------- *1 C881-K9 FTX18138205 License Information for 'c800' License Level: advipservices Type: Permanent Next reboot license Level: advipservices Configuration register is 0x2102 Router#
But here you can see our identity-challenged router doesn’t display it’s serial number:
Router#show version . . . Cisco 881 (MPC8300) processor (revision 1.0) with 236544K/25600K bytes of memory. Processor board ID . . . Router#
Thinking this could possibly be a bug in the IOS, I tried a couple more commands to see if I coax the router into telling me who it was:
Router#show diag . . . Chassis Serial Number : Product (FRU) Number : CISCO881-K9 . . . Router#
Router#show inventory NAME: "881", DESCR: "881 chassis, Hw Serial#: , Hw Revision: 1.0" PID: CISCO881-K9 , VID: V01 , SN: Router#
As you can plainly see, this router clearly doesn’t know who it is. I could manually set the serial number in the configuration but at this point, I don’t trust this router enough to put it into production. When I need to know what we have deployed in the field, I don’t want a router giving me any more difficulties than they already do.
I think we’ll be sending this one back to be “re-educated.” 🙂