A bug exists within the Cisco MIB files that has an inconsistency for sysUptime.
To replicate the problem, run the below SNMP command against the specific CISCO model to show uptime.
[/usr/local/iris]$ snmpwalk -v 2c -c examplestring 192.168.255.255 188.8.131.52.184.108.40.206
DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (66988960) 7 days, 18:04:49.60
Then log into your router and run:
Cisco IOS Software, s72033_rp Software (s72033_rp-ADVENTERPRISEK9_WAN-M), Version 12.2(33)SXI10, RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2012 by Cisco Systems, Inc.
Compiled Thu 13-Sep-12 22:28 by prod_rel_team
ROM: System Bootstrap, Version 12.2(17r)SX7, RELEASE SOFTWARE (fc1)
CISCO-EXAMPLE-SWITCH uptime is 6 weeks, 6 days, 13 hours, 2 minutes
Uptime for this control processor is 6 weeks, 6 days, 12 hours, 59 minutes
Time since CISCO-EXAMPLE-SWITCH switched to active is 6 weeks, 6 days, 12 hours, 58 minutes
System returned to ROM by reload (SP by reload)
You will notice actual uptime from the router differs from the SNMP uptime value, this is due to a bug in the cisco firmware.
Here is an example of an Iris uptime graph which hit the uptime bug. Even though the router appeared to have rebooted on Wednesday at 12pm, it was in fact never rebooted.
Below is the bug reference on Cisco’s website (Link to the Bug Report):
If you require assistance verifying this bug, please contact firstname.lastname@example.org with the necessary information.