244 PowerConnect B-Series FCX Configuration Guide
53-1002266-01
Configuring STP related features
8
FIGURE 38 Handshake completed after election of new root port
Recall that Switch 200 sent the agreed flag to Port4/Switch 60 and not to Port1/Switch 100 (the
port that connects Switch 100 to Switch 200). Therefore, Port1/Switch 100 does not go into
forwarding state instantly. It waits until two instances of the forward delay timer expires on the port
before it goes into forwarding state.
At this point the handshake between the Switch 60 and Switch 200 is complete.
The remaining bridges (Switch 300 and Switch 400) may have to go through the reroot handshake
if a new Root port needs to be assigned.
Convergence in a simple topology
The examples in this section illustrate how 802.1W convergence occurs in a simple Layer 2
topology at start-up.
The remaining examples assume that the appropriate handshake mechanisms occur as port roles
and states change.
Convergence at start up
In Figure 39, two bridges Switch 2 and Switch 3 are powered up. There are point-to-point
connections between Port3/Switch 2 and Port3/Switch 3.
Switch 100
Port2
Designated
port
Port2
Root port
Switch 60
Port4
Designated port
Port1
Proposing
Port1
Alternate port
Port4
Root port
Switch 200
Port2
Port2
Port3
Port3
Proposing Proposing
Switch 300
Switch 400
