Check SNMP Cisco Traffic
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Check Traffic Usage of an Interface on a Cisco Device
Check Traffic Usage of an Interface on a Cisco Device

This is a bit tricky, because cisco's snmp counter are independent from the cli output.
The snmp counters can't be reset at runtime, they online reset themself at reboot.
So in addition to the snmp values we get, we need to calculate....

We save the last check results/sums in a text file so make sure you set "tmpfile" below.
Please create it, fill in 4 zeros and make sure it is writable by the user that nagios runs as

$ touch /home/nagios/check_snmp_cisco_traffic.txt
$ echo 0 0 0 0> /home/nagios/check_snmp_cisco_traffic.txt
$ chown nagios:nagios /home/nagios/check_snmp_cisco_traffic.txt

This plugin currently only uses HC/64bit counter, because 32bit begin from zero too often.
You also have to find out the interface number yourself, i don't, yet, want the script to
search for it every runtime. Just snmpwalk your device like this:

$ snmpwalk -v2c -c community-string HOST 1.3.6.1.2.1.31.1.1.1.1
IF-MIB::ifName.1 = STRING: Fa0
This -^- is the interface-number

Version 0.1, Copyright (c) 2008 by Michael Boehm

TODO:
-testing
-maybe accepting Interface descriptions as argument
-maybe include check for 32bit counter