Port Roles - Avaya C360 Installation And Configuration Manual

Improvement in the time it takes to propagate TC information. Specifically, TC information
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does not have to be propagated all the way back to the Root Bridge (and back) to be
changed.
Origination of BPDUs on a port-by-port basis.
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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
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Designated port - corresponding port on the remote bridge of the local root port
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Alternate port - an alternate route to the root
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Backup port - an alternate route to the network segment
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The RSTP algorithm 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 may be rapidly
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 provides a means of fast network convergence after a topology change. It does this by
assigning different treatments to different port types. The port types and the treatment they
receive follow:
Edge ports - Setting a port to "edge-port" admin state indicates that this port is connected
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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 all ports is "edge-port".
Note:
You must manually configure uplink and backbone ports (including LAG logical
Note:
ports) to be "non-edge" ports, using the CLI command set port edge admin
state.
Point-to-point Link ports - This port type applies only to ports interconnecting RSTP
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compliant switches and is used to define whether the devices are interconnected using
shared Ethernet segment or point-to-point Ethernet link. RSTP convergence is faster when
switches are connected using point-to-point links. The default setting for all ports -
automatic detection of point-to-point link - is sufficient for most networks.
Spanning Tree Protocol
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