Configuration Guide User guide

1120 FastIron Configuration Guide
53-1002494-02
STP feature configuration
Handshake when a root port has been elected
If a non-root bridge already has a Root port, 802.1W uses a different type of handshake. For
example, in Figure 133, a new root bridge is added to the topology.
FIGURE 133 Addition of a new root bridge
The handshake that occurs between Switch 60 and Switch 100 follows the one described in the
previous section (“Handshake when no root port is elected” on page 1115). The former root bridge
becomes a non-root bridge and establishes a Root port (Figure 134).
However, since Switch 200 already had a Root port in a forwarding state, 802.1W uses the
Proposing -> Proposed -> Sync and Reroot -> Sync and Rerooted -> Rerooted and Synced ->
Agreed handshake:
Switch 100
Port2
Designated
port
Switch 60
Port4
Designated port
Port2
Port1
Root port
Port4
Port3
Port2
Switch 200
Port2
Port3
Switch 300
Switch 400
Port1
Designated port