OIDs

From GEANT2-JRA1 Wiki

How stable are the OIDs?

Do they change ofter the OID of a counter that you are monitoring? Yes.

Juniper

JUNOS take care that an interface has always the same OID (even after a router reboot).
Tim Streater states: You had to save the snmp-id file and restore it after. (Any confirmation about it?)
Joe Metzger believes that Juniper OID's can be reset if you swapped REs. (Any confirmation about it?)

History (non exaustive!)

• For GEANT, in 2001, there was change of OID Juniper modify the MIBs by adding .0.0 in the middle of an OID of the firewall filters counters (equivalent to ACL counter).

Cisco

OID (really, the index used by SNMP on OIDs that are tables) would change on Cisco equipment if the configuration was changed (adding/deleting an interface). This was true of the 12008's used by Abilene that ran something like Cisco IOS 12.0.x(S).

Cisco actually solved this problem in 2003 or 2004 by adding the snmp-server ifindex persist command to IOS. This work for most devices. http://www.cisco.com/warp/public/477/SNMP/ifIndex_Persistence.html This will store the ifindex associated with all physical and logical interfaces somewhere in NVRAM so it can survive a reboot. Removing physical interfaces or deleting logical interfaces do not change the OID of a interface after a reboot anymore.

• Surfnet has been using this feature with success for at least a year now.
• ESnet dropped it because it was causing some routers to hang during reboots.

Automation

ESnet deals with changes in a mostly automated fashion. We have a home-grown application that inspects all of their equipment on a daily basis and adjusts the SNMP collection system. It takes care of most common events such as OID changes, interfaces and sub-interfaces being added or deleted, IP address changes and interface description changes. It requires a simple manual step for some more significant changes (that we were not comfortable fully automating.)