Users Guide

• If the DHCP server is located on the ToR and the VLTi (ICL) is down due to a failed link when a VLT node is rebooted in BMP mode, it is
not able to reach the DHCP server, resulting in BMP failure.
• If the source is connected to an orphan (non-spanned, non-VLT) port in a VLT peer, the receiver is connected to a VLT (spanned) port-
channel, and the VLT port-channel link between the VLT peer connected to the source and TOR is down, trac is duplicated due to
route inconsistency between peers. To avoid this scenario, Dell Networking recommends conguring both the source and the receiver
on a spanned VLT VLAN.
• Bulk synchronization happens only for global IPv6 Neighbors; link-local neighbor entries are not synced.
• If all of the following conditions are true, MAC addresses may not be synced correctly:
– VLT peers use VLT interconnect (VLTi)
– Sticky MAC is enabled on an orphan port in the primary or secondary peer
– MACs are currently inactive
If this scenario occurs, use the clear mac-address-table sticky all command on the primary or secondary peer to
correctly sync the MAC addresses.
• If static ARP is enabled on only one VLT peer, entries may be overwritten during bulk sync.
• In VLT, non-default VRF is not supported on LM/LP physical or port-channel ports.
• Routing with non-spanned VLAN is not supported.
Conguration Notes
VLT requires that you enable the feature and then congure the same VLT domain, backup link, and VLT interconnect on both peer
switches. When you congure VLT, the following conditions apply.
• VLT domain
– A VLT domain supports two chassis members, which appear as a single logical device to network access devices connected to VLT
ports through a port channel.
– A VLT domain consists of the two core chassis, the interconnect trunk, backup link, and the LAG members connected to attached
devices.
– Each VLT domain has a unique MAC address that you can congure using the system-mac command. If you do not specify a
MAC address, VLT uses the primary peer’s MAC address by default.
– ARP tables are synchronized between the VLT peer nodes.
– VLT peer switches operate as separate chassis with independent control and data planes for devices attached on non-VLT ports.
– One chassis in the VLT domain is assigned a primary role; the other chassis takes the secondary role. The primary and secondary
roles are required for scenarios when connectivity between the chassis is lost. VLT assigns the primary chassis role according to the
lowest MAC address. You can congure the primary role.
– In a VLT domain, the peer switches must run the same Dell Networking OS version.
– Separately congure each VLT peer switch with the same VLT domain ID and the VLT version. If the system detects mismatches
between VLT peer switches in the VLT domain ID or VLT version, the VLT Interconnect (VLTi) does not activate. To nd the reason
for the VLTi being down, use the show vlt mismatch command to verify that there are mismatch errors, then use the show
vlt brief command on each VLT peer to view the VLT version on the peer switch. If the VLT version is more than one release
dierent from the current version in use, the VLTi does not activate.
– The chassis members in a VLT domain support connection to orphan hosts and switches that are not connected to both switches in
the VLT core.
• VLT interconnect (VLTi)
– The VLT interconnect must consist of either 10G or 40G ports. A maximum of eight 10G or four 40G ports is supported. A
combination of 10G and 40G ports is not supported.
– A VLT interconnect over 1G ports is not supported.
– The port channel must be in Default mode (not Switchport mode) to have VLTi recognize it.
– The system automatically includes the required VLANs in VLTi. You do not need to manually select VLANs.
– VLT peer switches operate as separate chassis with independent control and data planes for devices attached to non-VLT ports.
– Port-channel link aggregation (LAG) across the ports in the VLT interconnect is required; individual ports are not supported. Dell
Networking strongly recommends conguring a static LAG for VLTi.
– The VLT interconnect synchronizes L2 and L3 control-plane information across the two chassis.
– The VLT interconnect is used for data trac only when there is a link failure that requires using VLTi in order for data packets to
reach their nal destination.
Virtual Link Trunking (VLT)
1085