Reference Guide

VLT and Stacking
You cannot enable stacking S5000 units with VLT.
If you enable stacking on a unit on which you want to enable VLT, first remove the unit from the existing
stack. For information about how to remove a unit from a stack, refer to Remove a Switch from a Stack.
After you remove the unit, you can configure VLT on the unit.
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 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 apply, 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.
Virtual Link Trunking (VLT)
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