STP Message Age

The Message Age is a value contained within BPDUs which are used by the Spanning Tree Protocol (STP). The full contents of a BPDU can be found here: STP contents of a BPDU.

The Message Age is a value found within BPDUs that starts off at 0 when it is sent from the root bridge, and is incremented by one every time it passes through a non-root bridge. Once the Message Age reaches the Max Age value, the BPDU is discarded. It works kind of like a TTL found in IP packets, to prevent BPDUs from being relayed forever in a topology.


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