How does the IOS calculate the ifindex?

[has3]

We are trying to understand the process that the IOS uses to calculate the SNMP ifindex. We have a process that we use to update our NMS tool to record ifindex changes, but we would to understand the process used to calculate the ifindex. Does anyone have any insight on this?

[jegrimm]

Here it goes,

This is not a static list, it changes when interfaces (or sub-interfaces) are added. This also can change each time a reboot occurs. It seems to place the order based upon the type of interfaces (physical, controllers, physical->logical, sub)..

Check out the Performance and Fault Management pub by Cisco Press for more info.

jim