Dell Force10 Z9000 FTOS Configuration Guide for Z9000 System - Page 927

Sample RSTP Configuration Using Figure 48-1 as a sample VLT topology, the primary VLT switch will send BPDUs to an access device (switch or server) with its own RSTP bridge ID. BPDUs generated by an RSTP-enabled access device are only processed by the primary VLT switch. The secondary VLT switch tunnels the BPDUs that it receives to the primary VLT switch over the VLT interconnect. Only the primary VLT switch determines the RSTP roles and states on VLT ports, and ensures that the VLT interconnect link is never blocked. In case of a primary VLT switch failure, the secondary switch starts sending BPDUs with its own bridge ID and inherits all the port states from the last synchronization with the primary switch. An access device never detects the change in primary/secondary roles and does not see it as a topology change. The following figures show an example of the RSTP configuration that you must perform on each peer switch to prevent forwarding loops. Figure 48-2. Configuring RSTP on VLT Peers to Prevent Forwarding Loops (VLT Peer 1) FTOS_VLTpeer1(conf)#protocol spanning-tree rstp FTOS_VLTpeer1(conf-rstp)#no disable FTOS_VLTpeer1(conf-rstp)#bridge-priority 4096 Figure 48-3. Configuring RSTP on VLT Peers to Prevent Forwarding Loops (VLT Peer 2) FTOS_VLTpeer2(conf)#protocol spanning-tree rstp FTOS_VLTpeer2(conf-rstp)#no disable FTOS_VLTpeer2(conf-rstp)#bridge-priority 0 VLT Configuration Procedure To configure virtual link trunking and create a VLT domain in which two S4810 or Z9000 switches are physically connected and treated as a single port channel by access devices, you must configure the following settings on each VLT peer device: Prerequisite: Before you begin, make sure that both VLT peer switches are running the same FTOS version and are configured for RSTP as described in Chapter 38, Rapid Spanning Tree Protocol (RSTP). For VRRP operation, ensure that VRRP groups and L3 routing on each VLT peer are configured as described in Virtual Router Redundancy Protocol (VRRP). 1. Configure the VLT interconnect for the VLT domain. The primary and secondary switch roles in the VLT domain are automatically assigned after both sides of the VLTi are configured. Note: If a third-party ToR unit is used, Dell Force10 recommends using static LAGs on the VLTi between VLT peers to avoid potential problems if the VLT peers are rebooted. 2. Enable VLT and create a VLT domain ID. VLT automatically selects a system MAC address. 3. Configure a backup link for the VLT domain. Virtual Link Trunking (VLT) | 927