Quick Reference Guide

132 PowerConnect B-Series TI24X Configuration Guide

53-1002269-02

Configuring STP related features

For example, Port3/Switch 2 in Figure 21, fails. Port4/Switch 3 becomes the new Root port.

Port4/Switch 3 sends an RST BPDU with a TCN to Port4/Switch 4. To propagate the topology

change, Port4/Switch 4 then starts a TCN timer on itself, on the bridge Root port, and on other

ports on that bridge with a Designated role. Then Port3/Switch 4 sends RST BPDU with the TCN to

Port4/Switch 2. (Note the new active Layer 2 path in Figure 21.)

FIGURE 21 Beginning of topology change notice

Switch 2 then starts the TCN timer on the Designated ports and sends RST BPDUs that contain the

TCN as follows (Figure 22):

• Port5/Switch 2 sends the TCN to Port2/Switch 5

• Port4/Switch 2 sends the TCN to Port4/Switch 6

Bridge priority = 1000

Bridge priority = 200

Bridge priority = 60

Bridge priority = 900

Bridge priority = 400

Bridge priority = 300

Port2 Port2

Port2

Port3

Port4

Port5

Port 5

Port5

Port7 Port8

Indicates the active Layer 2 path

Indicates direction of TCN

Switch 1

Switch 2

Switch 5

Switch 3

Switch 4

Switch 6