HP ProCurve Secure 7000dl Series Basic Management And Configuration Manual page 515

Bridging—Transmitting Non-IP Traffic or Merging Two Networks
Configuring Spanning Tree
(although this is not a typical application for the router). Important configu-
rations for edge ports are BPDU guards and filters which keep the router from
receiving BPDUs from user software or rogue devices.
Blocking ports are divided into backup and alternate ports. Backup ports
provide a redundant connection to the root through a different device. Alter-
nate ports provide a redundant connection to the root through the same
device. If the root port goes down, alternate ports are allowed to move rapidly
into the forwarding state.
Ports on a point-to-point connection can use the rapid sync method to move
into the forwarding state. On the ProCurve Secure Router, ports will almost
always be on point-to-point connections. You can configure this setting, or you
can leave the interface at its default auto setting, which defines full-duplex
interfaces as point-to-point ports.
Sync. STP assumes that devices best decide which ports to activate by
collecting a great deal of information about the network. Therefore, it sets
conservative timers for listening for TCN BPDUs. Ports were forced to spend
30 seconds passing through the listening and learning phases before they
could begin to forward user traffic.
Many devices now connect through point-to-point connections rather than
through shared media. RSTP relies on the fact that the single neighbor at the
other end can refuse to activate a link if it has a better connection. Rather than
wait 30 seconds collecting information, a port can start forwarding user traffic
after a single rapid exchange with its neighbor.
10-15