Dell PowerConnect B-RX BigIron RX Series Configuration Guide v02.7.02 - Page 429

State machines 13 • Agreed - The Root port sends back an RST BPDU containing an agreed flag to its peer Designated port and moves into the forwarding state. When the peer Designated port receives the RST BPDU, it rapidly transitions into a forwarding state. FIGURE 46 Agree stage Switch 100 Root Bridge RST BPDU sent with an Agreed flag Port1 Designated port Forwarding Port1 Root port Synced Forwarding BigIron Switch 200 Port2 Synced Discarding Port3 Synced Discarding Switch 300 Port2 Port3 Switch 400 Indicates a signal At this point, the handshake mechanism is complete between Switch 100, the root bridge, and Switch 200. Switch 200 updates the information on the Switch 200's Designated ports (Port2 and Port3) and identifies the new root bridge. The Designated ports send RST BPDUs, containing proposal flags, to their downstream bridges, without waiting for the hello timers to expire on them. This process starts the handshake with the downstream bridges. For example, Port2/Switch 200 sends an RST BPDU to Port2/Switch 300 that contains a proposal flag. Port2/Switch 300 asserts a proposed signal. Ports in Switch 300 then set sync signals on the ports to synchronize and negotiate their roles and states. Then the ports assert a synced signal and when the Root port in Switch 300 asserts it is synced signal, it sends an RST BPDU to Switch 200 with an agreed flag. This handshake is repeated between Switch 200 and Switch 400 until all Designated and Root ports are in forwarding states. BigIron RX Series Configuration Guide 357 53-1001810-01