The max-age command indicates how many hops a BPDU can traverse the network starting from the root bridge. The message age field in a BPDU transmitted by the root bridge is initialized to 0. Each other bridge takes the message_age value from BPDUs received on their root port and increment this value by 1. Therefore, the message_age reflects the distance from the root bridge. BPDUs with a message age exceeding max-age are ignored.
STP uses the max-age value configured in the root bridge. This value is propagated to the other bridges by the BPDUs. The default value of max-age is 20. This parameter can be modified within a range of 6 to 40, limited by the standard STP parameter interaction formulas.
CLI syntax:
config>service>vpls service-id# stp
max-age max-info-age