Spanning Tree Per Port; Rapid Spanning Tree Protocol (Rstp) - Avaya G250 Administration

The relative priority of each port.
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The cost of each port.
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After these values are assigned, bridges multicast and process the formatted frames (called
Bridge Protocol Data Units, or BPDUs) to derive a single, loop-free topology throughout the
extended network. The bridges exchange BPDU frames quickly, minimizing the time that
service is unavailable between hosts.

Spanning tree per port

Spanning tree can take up to 30 seconds to open traffic on a port. This delay can cause
problems on ports carrying time-sensitive traffic. You can therefore enable or disable spanning
tree in the G350 on a per-port basis to minimize this effect.

Rapid Spanning Tree Protocol (RSTP)

About the 802.1w (RSTP) standard
The enhanced feature set of the 802.1w standard includes:
Bridge Protocol Data Unit (BPDU) type 2
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New port roles: Alternate port, Backup port
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Direct handshaking between adjacent bridges regarding a desired topology change (TC).
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This eliminates the need to wait for the timer to expire.
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 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.
Configuring spanning tree (G350 only)
Issue 1.1 June 2005 233