STP - Max Age vs Message Age

When implementing STP, there are two values that are used to aid in its operation: Max Age and Message Age. Although these are different, they are related and they work together to fulfil their purpose.

These should not be confused with aging time.

The age timer is used to determine for how long a particular BPDU that has arrived is valid and starts counting down as soon as the BPDU has arrived. The maximum value of the age timer is the Max Age.

The age timer starts its countdown at Max Age minus the message age that is received in that configuration BPDU.

Links:

https://forum.networklessons.com/t/introduction-to-spanning-tree/853/213?u=lagapidis

https://forum.networklessons.com/t/introduction-to-spanning-tree/853/212?u=lagapidis

https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/19120-122.html#anc6