Administrator Guide

VLT Bandwidth Monitoring
When bandwidth usage of the VLTi (ICL) exceeds 80%, a syslog error message (shown in the following message) and an SNMP trap are
generated.
%STKUNIT0-M:CP %VLTMGR-6-VLT-LAG-ICL: Overall Bandwidth utilization of VLT-ICL-LAG (port-
channel 25)
crosses threshold. Bandwidth usage (80 )
When the bandwidth usage drops below the 80% threshold, the system generates another syslog message (shown in the following
message) and an SNMP trap.
%STKUNIT0-M:CP %VLTMGR-6-VLT-LAG-ICL: Overall Bandwidth utilization of VLT-ICL-LAG (port-
channel 25)
reaches below threshold. Bandwidth usage (74 )VLT show remote port channel status
VLT and Stacking
You cannot enable stacking on the units with VLT.
If you enable stacking on a unit 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 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 IPv6
The following features have been enhanced to support 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.
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)