Dell N3200-ON EMC Networking N-Series Switches CLI Reference Guide version 6.7 - Page 854

priority to 49152. Path costs have an additional 3000 added when DRC is enabled. This reduces the probability that the switch will become the root switch. DRC immediately changes to an alternate root port on detecting a root port failure and change the new root port directly to the forwarding state. A TCN is sent for this event. After a switchover to an alternate port (new root port), DRC multicasts a gratuitous frame on the new root port on behalf of each attached machine so that the rest of the network knows to use the secondary link to reach that machine. DRC is disabled when the administrator modifies the spanning-tree priority of a VLAN and is re-enabled only when the default priority is restored. Configuration of the bridge priority is given preference over configuration of the root primary or root secondary configuration, which is given preference over the configuration of DirectLink Rapid Convergence. RSTP-PV embeds support for IRC and DRC. There is no provision to enable or disable these features in RSTP-PV configured switches. DRC is most useful for enterprise wiring-closet topologies with a limited number of VLANs. Do not enable DRC on backbone or distribution layer switches as DRC is not capable of completing the reconfiguration of large networks within the max age time. Example console(config)#spanning-tree uplinkfast spanning-tree vlan Use the spanning-tree vlan command to enable per VLAN spanning tree on a VLAN. Use the no form of the command to remove the VLAN as a separate spanning tree instance. Syntax spanning-tree vlan {vlan-list} no spanning-tree vlan {vlan-list} Layer 2 Switching Commands 854