Users Guide
Primary and Secondary VLT Peers
Primary and Secondary VLT Peers are supported on the Aggregator.
To prevent issues when connectivity between peers is lost, you can designate Primary and Secondary roles for VLT peers . You can elect or
congure the Primary Peer. By default, the peer with the lowest MAC address is selected as the Primary Peer.
If the VLTi link fails, the status of the remote VLT Primary Peer is checked using the backup link. If the remote VLT Primary Peer is available,
the Secondary Peer disables all VLT ports to prevent loops.
If all ports in the VLTi link fail or if the communication between VLTi links fails, VLT checks the backup link to determine the cause of the
failure. If the failed peer can still transmit heartbeat messages, the Secondary Peer disables all VLT member ports and any Layer 3
interfaces attached to the VLAN associated with the VLT domain. If heartbeat messages are not received, the Secondary Peer forwards
trac assumes the role of the Primary Peer. If the original Primary Peer is restored, the VLT peer reassigned as the Primary Peer retains
this role and the other peer must be reassigned as a Secondary Peer. Peer role changes are reported as SNMP traps.
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 with VLT.
If you enable stacking on a unit on which you want to enable VLT, you must rst remove the unit from the existing stack. After you remove
the unit, you can congure VLT on the unit.
VLT and IGMP Snooping
When conguring IGMP Snooping with VLT, ensure the congurations on both sides of the VLT trunk are identical to get the same
behavior on both sides of the trunk.
When you congure 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 conguration, 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 trac.
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PMUX Mode of the IO Aggregator