Dell PowerConnect B-RX BigIron RX Series Configuration Guide v02.7.02 - Page 450

13 Configuring RSTP parameters TABLE 76 Link speed Recommended path cost values of RSTP (Continued) Recommended (default) RSTP path cost values 1 Gigabit per second 10 Gigabits per second 100 Gigabits per second 1 Terabits per second 10 Terabits per second 20,000 2,000 200 20 2 Recommended RSTP path cost range 2,000 - 200,000,000 200 - 20,000 20 - 2,000 2 - 200 1 - 20 The priority parameter specifies the preference that RSTP gives to this port relative to other ports for forwarding traffic out of the topology. You can specify a value from 0 - 655352, in increments of 4. If you enter a value that is not divisible by four the software rounds to the nearest value that is. The default is 128 (the terminal shows this too). A higher numerical value means a lower priority; thus, the highest priority is 8. Set the admin-edge-port to enabled or disabled. If set to enabled, then the port becomes an edge port in the domain. Set the admin-pt2pt-mac to enabled or disabled. If set to enabled, then a port is connected to another port through a point-to-point link. The point-to-point link increases the speed of convergence. This parameter, however, does not auto-detect whether or not the link is a physical point-to-point link. The force-migration-check parameter forces the specified port to sent one RST BPDU. If only STP BPDUs are received in response to the sent RST BPDU, then the port will go return to sending STP BPDUs. Example Suppose you want to enable RSTP on a system with no active port-based VLANs and change the hello-time from the default value of 2 to 8 seconds. Additionally, suppose you want to change the path and priority costs for port 5 only. To do so, enter the following commands. BigIron RX(config)# spanning-tree 802-1w hello-time 8 BigIron RX(config)# spanning-tree 802-1w ethernet 5 path-cost 15 priority 64 Fast port span When STP is running on a device, message forwarding is delayed during the spanning tree recalculation period following a topology change. The STP forward delay parameter specifies the period of time a bridge waits before forwarding data packets. The forward delay controls the listening and learning periods of STP reconvergence. You can configure the forward delay to a value from 4 - 30 seconds. The default is 15 seconds. Thus, using the standard forward delay, convergence requires 30 seconds (15 seconds for listening and an additional 15 seconds for learning) when the default value is used. This slow convergence is undesirable and unnecessary in some circumstances. The Fast Port Span feature allows certain ports to enter the forwarding state in four seconds. Specifically, Fast Port Span allows faster convergence on ports that are attached to end stations and thus do not present the potential to cause Layer 2 forwarding loops. Because the end stations cannot cause 378 BigIron RX Series Configuration Guide 53-1001810-01