The switch stores the peer MAC and IP address pair in its local configuration file and restores the configuration if the peer does not restore after a simultaneous restart of both RSMLT-peer switches.
The RSMLT edge support feature adds an enhancement whereby the peer MAC (for the IP on the VLAN) is committed to the config.cfg file after you use the save config command. If you power off both devices, and then power up only one of them, that single device can still take ownership of its peer IP on that VLAN even if it has not seen that peer switch since it started. This enhancement is necessary if you configure the peer (the device which is still down) IP as the default gateway in end stations.
If you enable RSMLT edge support, you must also ensure that the hold-up timer for RSMLT on those edge VLANs equals infinity (9999). This timer value ensures that if one cluster device fails, the remaining cluster device maintains ownership of the failed peer IP indefinitely.
The edge VLAN can be tagged over SMLT links, single attached links, or more SMLT links.
Important
If you clear the peer information the device can stop forwarding for the peer.
RSMLT implementation does not use a virtual IP address but instead uses physical IP addresses for redundancy. At the same time, you can deploy RSMLT in either routed configurations, or edge configurations, where you previously used VRRP (and back-up master). Previously, if a power outage occurred or a shutdown of both switches within a dual core vIST pair, only one device came back up. Clients using the powered-off device IP/MAC as the default gateway lost connectivity to the network. In such a scenario, even with RSMLT enabled on the device, it cannot act as a backup for the peer as it was unaware of the peer IP or MAC address.
After both the dual core vIST switches come back, the vIST is operational. If an RSMLT peer-enabled message is received from the peer, normal RSMLT operation occurs.
If the peer has either an IP or MAC change, you must save the configuration for the RSMLT edge support to operate correctly. However, if the vIST peer up message is not received (for example, if you do not enable RSMLT properly), and you enable the RSMLT edge support flag, the RSMLT hold-down timer starts and permits routing protocols to converge; during this time user operation can be affected. After the hold-down timer expires, saved peer information is picked up and the device starts to act as backup for the peer by adding the previously saved MAC and ARP records.
The hold-up timer starts and after this timer expires the previously added MAC and ARP records are deleted and the device stops acting as backup for the peer, as the peer is not running proper RSMLT for the VLAN. The RSMLT is a parameter for each VLAN, and therefore all affects are on an individual VLAN basis, not necessarily a global device. Edge support mode uses the local values of the hold-down timer (default value of 60 seconds) and hold-up timer (default value of 180 seconds).