Avaya G250 Administration page 323

Port roles
At the center of RSTP — specifically as an improvement over STP (802.1d) — are the roles that
are assigned to the ports. There are four port roles:
Root port — port closest to the root bridge
●
Designated port — corresponding port on the remote bridge of the local root port
●
Alternate port — an alternate route to the root
●
Backup port — an alternate route to the network segment
●
The RSTP algorithm usually makes it possible to change port roles rapidly through its fast
topology change propagation mechanism. For example, a port in the blocking state can be
assigned the role of alternate port. When the backbone of the network fails the port can rapidly
be changed to forwarding.
Whereas the STA passively waited for the network to converge before turning a port into the
forwarding state, RSTP actively confirms that a port can safely transition to forwarding without
relying on any specific, programmed timer configuration.
RSTP port types
RSTP provides a means of fast network convergence after a topology change. It does this by
assigning different treatments to different port types.
Edge ports — Setting a port to edge-port admin state indicates that this port is connected
●
directly to end stations that cannot create bridging loops in the network. These ports
transition quickly to forwarding state. However, if BPDUs are received on an Edge port, it's
operational state will be changed to non-edge-port and bridging loops will be avoided by
the RSTP algorithm. The default admin state of 10/100 M ports is edge-port.
Use the set port edge admin state command, followed by the module and port
number, or a range of port numbers, to specify whether or not a port is considered an edge
port. For example, the following command specifies that ports 5 to 13 on module 4 are
edge ports:
G350-001(super)# set port edge admin state 4/5-13 edge-port
The following command specifies that port 6 on module 6 is not an edge port:
G350-001(super)# set port edge admin state 6/6 non-edge-port
Use the show port edge state command, followed by the module and port number, to
display the edge state of the specified port. Use this command without specifying a module
number or port to display the edge state of all ports.
Non-edge ports — You must manually configure uplink and backbone ports to be
●
non-edge ports, using the set port edge admin state command.
Configuring spanning tree (G350 only)
Issue 3 February 2007 323