Typically, the first Switch Fabric (SF)/CPM card installed in a redundant SR-series router chassis assumes the role as active, regardless of being inserted in Slot A or B. The next CPM installed in the same chassis then assumes the role as the standby CPM. If two CPM are inserted simultaneously (or almost simultaneously) and are booting at the same time, then preference is given to the CPM installed in Slot A.
If only one CPM is installed in a redundant router device, then it becomes the active CPM regardless of the slot it is installed in.
The active and standby designations can be visually determined by LEDs on the CPM/CCM faceplate. See the appropriate platform Installation Guide for LED indicator details.
The following output shows that the CPM installed in Slot A is acting as the active CPM and the CPM installed in Slot B is acting as the standby.
The following is an example of the 7950 XRS output:
*A:7950 XRS-20# show card
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Card Summary
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Slot Provisioned Type Admin Operational Comments
Equipped Type (if different) State State
-------------------------------------------------------------------------------
1 xcm-x20 up provisioned
A cpm-x20 up up/active
B cpm-x20 up up/standby
===============================================================================
The following console message displays when a CPM boots, sees an active CPM, and becomes the standby CPM:
...
Slot A contains the Active CPM
This CPM (Slot B) is the Standby CPM