HP ProCurve 9304M Installation And Configuration Manual page 252

Installation and Basic Configuration Guide
For example, Port3/Routing Switch 2 in Figure 8.20, fails. Port4/Routing Switch 3 becomes the new Root port.
Port4/Routing Switch 3 sends an RST BPDU with a TCN to Port4/Routing Switch 4. To propagate the topology
change, Port4/Routing Switch 4 then starts a TCN timer on itself, on the bridge's Root port, and on other ports on
that bridge with a Designated role. Then Port3/Routing Switch 4 sends RST BPDU with the TCN to Port4/Routing
Switch 2. (Note the new active Layer 2 path in Figure 8.20.)
Figure 8.20 Beginning of Topology Change Notice
Routing Switch 1
Bridge priority = 1000
Port3
Port2
Routing Switch 3
Bridge priority = 300
8 - 46
Routing Switch 2
Bridge priority = 200
Port7
Port2 Port2
Port3
Port3
Port4 Port4
Routing Switch 4
Bridge priority = 400
Indicates the active Layer 2 path
Indicates direction of TCN
Port8
Port5
Port4
Port3
Port5 Port5
Routing Switch 5
Bridge priority = 60
Port2
Port3
Port3
Port4
Routing Switch 6
Bridge priority = 900