Cisco SNMP Monitoring

Cases for use

To store metrics about how your Cisco routers and swtiches are performing, you’ll probably find yourself needing to
enable SNMP. This protocol enables the gathering of statistics through MIBs (Management Information Bases) over the SNMP protocol.
You can then track bandwith utilisation to help plan upgrades, de-commissions, and the like.

Versions

v1 is all but completely unused.
v2c is the most common implementation. We’ll discuss that here and I’ll add a further section regarding v3 and it’s authentication options.

 Configuration

When retrieving statistics from the device, you don’t want interfaces re-numbering and changing otherwise your hard work
will be for nothing when you’re polling interfaces and they change on you after a reload or installation of a network module.

snmp-server ifindex persist

If you’re working in a large enough organisation to be able to personalise the systems so that you have areas of responsibility you can add
basic contact details for the devices.

snmp-server contact ITDept
snmp-server location TheLondonDungeon

Because you likely don’t want any system to be able to contact the device using SNMP, you can determine which systems should be able to poll the SNMP Server by creating an ACL.
Perhaps you have one server that you want to access SNMP on the device and an entire Management subnet.

ip access-list standard 10
 permit host 192.168.1.20
 permit 192.168.4.0 0.0.0.255

Consider the read-only community string you will use for your devices and configure this, along with the access-list and assign it a read-only permission.

snmp-server community <string> ro 10

You can now configure your monitoring device to poll all the routers and swtiches in your network to store statistics.

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