HP ProCurve 9304M Installation And Configuration Manual page 245

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.
NOTE: The remaining examples assume that the appropriate handshake mechanisms occur as port roles and
states change.
Convergence at Start Up
In Figure 8.14, two bridges Routing Switch 2 and Routing Switch 3 are powered up. There are point-to-point
connections between Port3/Routing Switch 2 and Port3/Routing Switch 3.
Figure 8.14 Convergence Between Two Bridges
At power up, all ports on Routing Switch 2 and Routing Switch 3 assume Designated port roles and are at
discarding states before they receive any RST BPDU.
Port3/Routing Switch 2, with a Designated role, transmits an RST BPDU with a proposal flag to Port3/Routing
Switch 3. A ports with a Designated role sends the proposal flag in its RST BPDU when they are ready to move to
a forwarding state.
Port3/Routing Switch 3, which starts with a role of Designated port, receives the RST BPDU and finds that it is
superior to what it can transmit; therefore, Port3/Routing Switch 3 assumes a new port role, that of a Root port.
Port3/Routing Switch 3 transmits an RST BPDU with an agreed flag back to Routing Switch 2 and immediately
goes into a forwarding state.
Port3/Routing Switch 2 receives the RST BPDU from Port3/Routing Switch 3 and immediately goes into a
forwarding state.
Now 802.1W has fully converged between the two bridges, with Port3/Routing Switch 3 as an operational root port
in forwarding state and Port3/Routing Switch 2 as an operational Designated port in forwarding state.
Configuring Spanning Tree Protocol (STP) and Advanced STP Features
Bridge priority = 1500
Routing Switch 2
Port3
Designated
port
Port3
Root port
Routing Switch 3
Bridge priority = 2000
8 - 39