Dell PowerConnect B-RX BigIron RX Series Configuration Guide v02.7.03 - Page 432

13 State machines • Proposing - The Designated port on the root bridge sends an RST BPDU packet to its peer port that contains a proposal flag. The proposal flag is a signal that indicates that the Designated port is ready to put itself in a forwarding state (Figure 43). The Designated port continues to send this flag in its RST BPDU until it is placed in a forwarding state (Figure 46) or is forced to operate in 802.1D mode. (Refer to "Compatibility of RSTP with 802.1D" on page 380) • Proposed - When a port receives an RST BPDU with a proposal flag from the Designated port on its point-to-point link, it asserts the Proposed signal and one of the following occurs (Figure 43): • If the RST BPDU that the port receives is superior to what it can transmit, the port assumes the role of a Root port. (Refer to "Bridges and bridge port roles" on page 353.) • If the RST BPDU that the port receives is inferior to what it can transmit, then the port is given the role of Designated port. NOTE Proposed will never be asserted if the port is connected on a shared media link. In Figure 43, Port3/Switch 200 is elected as the Root port FIGURE 43 Proposing and proposed stage Switch 100 Root Bridge RST BPDU sent with a Proposal flag Port2 Designated port Proposing Port1 Root port Proposed Switch 200 Port2 Port3 Switch 300 Port2 Port3 Switch 400 • Sync - Once the Root port is elected, it sets a sync signal on all the ports on the bridge. The signal tells the ports to synchronize their roles and states (Figure 44). Ports that are non-edge ports with a role of Designated port change into a discarding state. These ports have to negotiate with their peer ports to establish their new roles and states. 360 BigIron RX Series Configuration Guide 53-1001986-01