• If the DHCP server is located on the ToR and the VLTi (ICL) is down due to a failed link when a VLT nodeis 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 isconnected to a VLT (spanned) port-channel, and the VLT port-channel link between the VLT peerconnected to the source and TOR is down, traffic is duplicated due to route inconsistency betweenpeers. To avoid this scenario, Dell Networking recommends configuring both the source and thereceiver 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 inactiveIf this scenario occurs, use the clear mac-address-table sticky all command on the primaryor 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.Configuration NotesVLT requires that you enable the feature and then configure the same VLT domain, backup link, and VLTinterconnect on both peer switches. When you configure VLT, the following conditions apply.• VLT domain• A VLT domain supports two chassis members, which appear as a single logical device to networkaccess 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 LAGmembers connected to attached devices.• Each VLT domain has a unique MAC address that you can configure using the system-maccommand. If you do not specify a MAC address, VLT uses the primary peer’s MAC address bydefault.• ARP tables are synchronized between the VLT peer nodes.• VLT peer switches operate as separate chassis with independent control and data planes fordevices attached on non-VLT ports.• One chassis in the VLT domain is assigned a primary role; the other chassis takes the secondaryrole. The primary and secondary roles are required for scenarios when connectivity between thechassis is lost. VLT assigns the primary chassis role according to the lowest MAC address. You canconfigure the primary role.• In a VLT domain, the peer switches must run the same Dell Networking OS version.• Separately configure each VLT peer switch with the same VLT domain ID and the VLT version. Ifthe system detects mismatches between VLT peer switches in the VLT domain ID or VLT version,the VLT Interconnect (VLTi) does not activate. To find the reason for the VLTi being down, use theshow vlt mismatch command to verify that there are mismatch errors, then use the show vltbrief command on each VLT peer to view the VLT version on the peer switch. If the VLT versionis more than one release different 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 arenot 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 four40G ports is supported. A combination of 10G and 40G ports is not supported.Virtual Link Trunking (VLT) 1168
