Users Guide

• 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, traffic is duplicated due to route inconsistency between
peers. To avoid this scenario, Dell Networking recommends configuring both the source and the
receiver on a spanned VLT VLAN.
• Bulk Sync 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 you enable static ARP on only one VLT peer, entries may be overwritten during bulk sync.
• For multiple VLT LAGs configured on the same VLAN, if a host is learned on one VLT LAG and there is a
station move between LAGs, the link local address redirects to the VLTi link on one of the peers. If this
occurs, clear the link local address that is redirecting to the VLTi link.
• VLT Heartbeat is supported only on default VRFs.
• In a scenario where one hundred hosts are connected to a Peer1 on a non-VLT domain and traffic flows
through Peer1 to Peer2; when you move these hosts from a non-VLT domain to a VLT domain and send
ARP requests to Peer1, only half of these ARP requests reach Peer1, while the remaining half reach Peer2
(because of LAG hashing). The reason for this behavior is that Peer1 ignores the ARP requests that it
receives on VLTi (ICL) and updates only the ARP requests that it receives on the local VLT. As a result, the
remaining ARP requests still points to the Non-VLT links and traffic does not reach half of the hosts. To
mitigate this issue, ensure that you configure the following settings on both the Peers (Peer1 and Peer2):
arp learn-enable and mac-address-table station-move refresh-arp.
• In a topology in which two VLT peer nodes that are connected by a VLTi link and are connected to a
ToR switch using a VLT LAG interface, if you configure an egress IP ACL and apply it on the VLT LAG of
both peers using the deny ip any any command, the traffic is permitted on the VLT LAG instead of
being denied. The correct behavior of dropping the traffic on the VLT LAG occurs when VLT is up on
both the peer nodes. However, if VLT goes down on one of the peers, traffic traverses through VLTi and
the other peer switches it to the VLT LAG. Although egress ACL is applied on the VLT nodes to deny all
traffic, this egress ACL does not deny the traffic (switching traffic is not denied owing to the egress IP
ACL). You cannot use egress ACLs to deny traffic properly in such a VLT scenario.
• To support Q-in-Q over VLT, ICL is implicitly made as vlan-stack trunk port and the TPID of the
ICL is set as
8100.
• Layer 2 Protocol Tunneling is not supported in VLT.
Configuration Notes
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 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 create or VLT creates automatically.
Virtual Link Trunking (VLT) 1031