Dell Force10 MXL Blade MXL 10/40GbE Switch IO Module Configuration Guide - Page 586

www.dell.com | support.dell.com Modifying Interface STP Parameters You can set the port cost and port priority values of interfaces in Layer 2 mode. • Port cost is a value that is based on the interface type. 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. The default values are listed in Table 33-2. To change the port cost or priority of an interface, use the following commands: Task Change the port cost of an interface. Range: 0 to 65535 Default: see Table 33-2. Change the port priority of an interface. Range: 0 to 15 Default: 8 Command Syntax spanning-tree 0 cost cost Command Mode INTERFACE spanning-tree 0 priority priority-value INTERFACE To view the current values for interface parameters, use the show spanning-tree 0 command from EXEC privilege mode (Figure 33-5). Enabling PortFast The PortFast feature enables interfaces to begin forwarding traffic approximately 30 seconds sooner. Interfaces forward frames by default until they receive a BPDU that indicates that they should behave otherwise; they do not go through the Learning and Listening states. The bpduguard shutdown-on-violation option causes the interface hardware to be shutdown when it receives a BPDU. When you only implement bpduguard, although the interface is placed in an Error Disabled state when receiving the BPDU, the physical interface remains up and STP drops packets in the hardware after a BPDU violation. BPDUs are dropped in the software after receiving the BPDU violation. Caution: Enable PortFast only on links connecting to an end station. PortFast can cause loops if you enable it on an interface connected to a network. BPDU Filtering enabled on an interface, stops sending and receiving BPDUs on the port fast enabled ports. When BPDU guard and BPDU filter is enabled on the port, then BPDU filter takes the highest precedence. By default bpdu filtering on an interface is disabled. 584 | Spanning Tree Protocol (STP)