This attribute specifies how fast a bridge port changes its STP state
while progressing towards the forwarding state. It is also used as
agingTime to age dynamic entries in the forwarding table once a
topology change is detected. This attribute is used by all the bridges
participating in the spanning tree protocol, when this bridge is the root
bridge.
The following relationship is enforced as required by the IEEE 802.1d
standards document.
2 *(bridgeForwardDelay -1.0sconds) >= bridgeMaxAge.