Administrator Guide

VLT and High Availability
High availability (HA) support on VLT ensures seamless and uninterrupted flow of VLT features during RPM failure (failover).
When RPM failover happens, the new active RPM triggers a new VLT registration to its VLT peer. It ensures that the VLT node
with new active RPM receives all the VLT information from its VLT peer. When the standby RPM performs the check-in and
registration function (with the active RPM), the latter performs a bulk synchronization of all the peer VLT information. The
existing CLI configuration synchronized to the standby RPM ensures that the local VLT configurations are always available at
standby RPM as well. The VLT backup link functionality is also modified to manage the two management interfaces in a dual
RPM. A virtual management IP must be configured on the dual RPM VLT node to maintain uninterrupted VLT backup
functionality. For more information, refer to “VLT backup link” section in the Configuration Notes
VLT and IGMP Snooping
When configuring IGMP Snooping with VLT, ensure the configurations on both sides of the VLT trunk are identical to get the
same behavior on both sides of the trunk.
When you configure IGMP snooping on a VLT node, the dynamically learned groups and multicast router ports are automatically
learned on the VLT peer node.
VLT and Stacking
You cannot enable stacking on switches configured for VLT operation.
If you enable stacking on a Dell Networking switch on which you want to enable VLT, you must first remove the unit from the
existing stack. After you remove the unit, you can configure VLT on the switch.
VLT IPv6
The following features have been enhanced to support VLT on IPv6.
:
● VLT Sync — Entries learned on the VLT interface are synced on both VLT peers.
● Non-VLT Sync — Entries learned on non-VLT interfaces are synced on both VLT peers.
● Tunneling — Control information is associated with tunnel traffic so that the appropriate VLT peer can mirror the ingress
port as the VLT interface rather than pointing to the VLT peer’s VLTi link.
● Statistics and Counters — Statistical and counter information displays IPv6 information when applicable.
● Heartbeat — You can configure an IPv4 or IPv6 address as a backup link destination. You cannot use an IPv4 and an IPv6
address simultaneously. If you have a dual RPM, configure a virtual IP address(ipv4/ipv6) as backup link.
VLT Port Delayed Restoration
When a VLT node boots up, if the VLT ports have been previously saved in the start-up configuration, they are not immediately
enabled.
To ensure MAC and ARP entries from the VLT per node are downloaded to the newly enabled VLT node, the system allows time
for the VLT ports on the new node to be enabled and begin receiving traffic.
The delay-restore feature waits for all saved configurations to be applied, then starts a configurable timer. After the timer
expires, the VLT ports are enabled one-by-one in a controlled manner. The delay between bringing up each VLT port-channel is
proportional to the number of physical members in the port-channel. The default is 90 seconds.
To change the duration of the configurable timer, use the delay-restore command.
If you enable IGMP snooping, IGMP queries are also sent out on the VLT ports at this time allowing any receivers to respond to
the queries and update the multicast table on the new node.
This delay in bringing up the VLT ports also applies when the VLTi link recovers from a failure that caused the VLT ports on the
secondary VLT peer node to be disabled.
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Virtual Link Trunking (VLT)