Netgear XCM8806 Chassis User Manual - Page 551

NETGEAR 8800 User Manual • Is now a root port and no other ports have a recent role assignment that contradicts with its root port role. • Is a designated port and attaches to another bridge by a point-to-point link and receives an "agree" message from the other bridge port. • Is an edge port. An edge port is a port connected to a non-STP device and is in the forwarding state. The following sections provide more information about RSTP behavior. Root Port Rapid Behavior In Figure 41, the diagram on the left displays the initial network topology with a single bridge having the following: • Two ports are connected to a shared LAN segment. • One port is the designated port. • One port is the backup port. The diagram on the right displays a new bridge that: • Is connected to the LAN segment • Has a superior STP bridge priority • Becomes the root bridge and sends a BPDU to the LAN that is received by both ports on the old bridge Inital topology New topology Bridge Backup port Designated port Bridge Backup port Designated port LAN segment Superior STP bridge priority Root bridge EX_054 Figure 41. Example of Root Port Rapid Behavior If the backup port receives the BPDU first, STP processes this packet and temporarily elects this port as the new root port while the designated port's role remains unchanged. If the new root port is immediately put into the forwarding state, there is a loop between these two ports. To prevent this type of loop from occurring, the recent backup timer starts. The root port transition rule does not allow a new root port to be in the forwarding state until the recent backup timer expires. Chapter 18. STP | 551