Administrator Guide

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.
PIM-Sparse Mode Support on VLT
The designated router functionality of the PIM Sparse-Mode multicast protocol is supported on VLT peer switches for multicast sources
and receivers that are connected to VLT ports.
VLT peer switches can act as a last-hop router for IGMP receivers and as a first-hop router for multicast sources.
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Virtual Link Trunking (VLT)