Dell C1048P Port Extender Networking Configuration Guide for the C9000 Series - Page 810

Modifying Interface Parameters On interfaces in Layer 2 mode, you can set the port cost and port priority values. • Port cost - a value that is based on the interface type. The previous table lists the default values. The greater the port cost, the less likely the port is selected to be a forwarding port. • Port priority - influences the likelihood that a port is selected to be a forwarding port in case that several ports have the same port cost. To change the port cost or priority of an interface, use the following commands. • Change the port cost of an interface. INTERFACE mode spanning-tree rstp cost cost The range is from 0 to 65535. The default is listed in the previous table. • Change the port priority of an interface. INTERFACE mode spanning-tree rstp priority priority-value The range is from 0 to 15. The default is 128. To view the current values for interface parameters, use the show spanning-tree rstp command from EXEC privilege mode. Influencing RSTP Root Selection RSTP determines the root bridge, but you can assign one bridge a lower priority to increase the likelihood that it is selected as the root bridge. To change the bridge priority, use the following command. • Assign a number as the bridge priority or designate it as the primary or secondary root. PROTOCOL SPANNING TREE RSTP mode bridge-priority priority-value - priority-value The range is from 0 to 65535. The lower the number assigned, the more likely this bridge becomes the root bridge. The default is 32768. Entries must be multiples of 4096. Example of the bridge-priority Command A console message appears when a new root bridge has been assigned. The following example example shows the console message after the bridge-priority command is used to make R2 the root bridge (shown in bold). Dell(conf-rstp)#bridge-priority 4096 04:27:59: %SYSTEM-P:RP2 %SPANMGR-5-STP_ROOT_CHANGE: RSTP root changed. My Bridge ID: 4096:0001.e80b.88bd Old Root: 32768:0001.e801.cbb4 New Root: 4096:0001.e80b.88bd Configuring an EdgePort The EdgePort feature enables interfaces to begin forwarding traffic approximately 30 seconds sooner. In this mode an interface forwards frames by default until it receives a BPDU that indicates that it should behave otherwise; it does not go through the Learning and Listening states. The bpduguard shutdown-on-violation option causes the Rapid Spanning Tree Protocol (RSTP) 810