Dell PowerConnect B-RX BigIron RX Series Configuration Guide v02.7.02 - Page 435

Convergence in a simple topology 13 The Designated port on Switch 60 goes into a forwarding state once it receives the RST BPDU with the agreed flag. FIGURE 52 Handshake completed after election of new root port Switch 100 Port1 Port2 Root port Port2 Designated port Switch 60 Port4 Designated port Proposing Switch 200 Port2 Proposing Port1 Alternate port Port4 Root port Port3 Proposing Port2 Switch 300 Port3 Switch 400 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 RSTP 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. BigIron RX Series Configuration Guide 363 53-1001810-01