Dell PowerSwitch S4128F-ON OS10 Enterprise Edition User Guide Release 10.4.1.0 - Page 721

OS10(config)# vlt-domain 1 OS10(conf-vlt-1)# backup destination ipv6 1::1 vrf management interval 30 The following examples describe different cases where VLT backup link can be used: MAC and ARP not synchronized When VLTi fails, MAC address learnt after the failure is not synchronized with VLT peers. This leads to continuous flooding of traffic instead of unicast. Due to wrong hashing, ARP learning might fail leading to traffic being dropped. In the following illustration, after VLTi is down VLT peer 1 learns MAC address of Host 2. As VLTi link fails, the VLT peer1 is not synched up with the MAC address of Host2 . Due to this, if the traffic from Host1 is hashed to VLT peer2, then the VLT peer2 floods the traffic. Yet, the traffic would not reach Host2 as the VLT port between VLT peer 2 and Swicth 3 is down. When VLT backup link is enabled, the secondary VLT peer 2 identifies the node liveliness through the backup link. If the primary is up, the secondary peer brings down the VLT LAG ports. Now the traffic from Host1 reaches VLT peer 1 and then reaches the destination, that is Host2. In this case the traffic is unicasted instead of flooding, as shown in the following illustration. Virtual Link Trunking 721