Users Guide

The delay-restore feature waits for all saved congurations to be applied, then starts a congurable 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.
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.
VLT Routing
VLT routing is supported on the Aggregator.
Layer 2 protocols from the ToR to the server are intra-rack and inter-rack. No spanning tree is required, but interoperability with spanning
trees at the aggregation layer is supported. Communication is active-active, with no blocked links. MAC tables are synchronized between
VLT nodes for bridging and you can enable IGMP snooping.
Spanned VLANs
Any VLAN congured on both VLT peer nodes is referred to as a Spanned VLAN. The VLT Interconnect (VLTi) port is automatically added
as a member of the Spanned VLAN. As a result, any adjacent router connected to at least one VLT node on a Spanned VLAN subnet is
directly reachable from both VLT peer nodes at the routing level.
Non-VLT ARP Sync
In the Dell Networking OS version 9.2(0.0), ARP entries (including ND entries) learned on other ports are synced with the VLT peer to
support station move scenarios.
Prior to Dell Networking OS version 9.2.(0.0), only ARP entries learned on VLT ports were synced between peers.
Additionally, ARP entries resulting from station movements from VLT to non-VLT ports or to dierent non-VLT ports are learned on the
non-VLT port and synced with the peer node. The peer node is updated to use the new non-VLT port.
NOTE
: ARP entries learned on non-VLT, non-spanned VLANs are not synced with VLT peers.
Verifying a VLT Conguration
To monitor the operation or verify the conguration of a VLT domain, use any of the following show commands on the primary and
secondary VLT switches.
• Display information on backup link operation.
EXEC mode
show vlt backup-link
• Display general status information about VLT domains currently congured on the switch.
EXEC mode
show vlt brief
• Display detailed information about the VLT-domain conguration, including local and peer port-channel IDs, local VLT switch status, and
number of active VLANs on each port channel.
EXEC mode
show vlt detail
• Display the VLT peer status, role of the local VLT switch, VLT system MAC address and system priority, and the MAC address and
priority of the locally-attached VLT device.
PMUX Mode of the IO Aggregator
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