White Papers

Codes: * - Default VLAN, G - GVRP VLANs, R - Remote Port Mirroring VLANs, P - Primary, C
- Community, I - Isolated
O - Openflow
Q: U - Untagged, T - Tagged
x - Dot1x untagged, X - Dot1x tagged
o - OpenFlow untagged, O - OpenFlow tagged
G - GVRP tagged, M - Vlan-stack
i - Internal untagged, I - Internal tagged, v - VLT untagged, V - VLT tagged
NUM Status Description Q Ports
50 Active M Po10(Te 1/8)
M Po20(Te 1/20)
V Po1(Te 1/30-32)
DellEMC#
IPv6 Peer Routing in VLT Domains Overview
VLT enables the physical links between two devices that are called VLT nodes or peers, and within a VLT domain, to be
considered as a single logical link to external devices that are connected using LAG bundles to both the VLT peers. This
capability enables redundancy without the implementation of Spanning tree protocol (STP), thereby providing a loop-free
network with optimal bandwidth utilization.
IPv6 peer routing is supported on all the platforms that are compatible with IPv6 routing and support VLT. This functionality
performs the following operations:
● Forwarding control traffic to the correct VLT node when the control traffic reaches the wrong VLT node due to hashing at
the VLT LAG level on the ToR.
● Routing the data traffic which is destined to peer VLT node.
● Synchronizing neighbor entries learned on VLT VLAN interfaces between the primary and secondary node.
● Synchronizing the IP address of VLT VLAN interfaces between the VLT primary node and secondary node.
● Performing routing on behalf of peer VLT nodes for a configured time period when a peer VLT node goes down.
When you configure Layer 3 VLT peer routing using the peer-routing command in VLT DOMAIN mode, it applies for both
IPv4 and IPv6 traffic in VLT domains. Layer 3 VLT provides a higher resiliency at the Layer 3 forwarding level. Routed VLT
allows you to replace VRRP with routed VLT to route the traffic from the Layer 2 access nodes. With neighbor discovery (ND)
synchronization, both the VLT nodes perform Layer 3 forwarding on behalf of each other.
The neighbor entries are typically learned by a node using neighbor solicitation (NS) and ND messages. These NS or neighbor
advertisement (NA) messages can be either destined to the VLT node or to any nodes on the same network as the VLT
interface. These learned neighbor entries are propagated to another VLT node so that the peer does not need to relearn the
entries.
IPv6 Peer Routing
When you enable peer routing on VLT nodes, the MAC address of the peer VLT node is stored in the ternary content
addressable memory (TCAM) space table of a station. If the data traffic destined to a VLT node, node1, reaches the other
VLT node, node2, owing to LAG-level hashing in the ToR switch, it is routed instead of forwarding the packet to node1. This
processing occurs because of the match or hit for the entry in the TCAM of the VLT node2.
Synchronization of IPv6 ND Entries in a VLT Domain
Because the VLT nodes appear as a single unit, the ND entries learned via the VLT interface are expected to be the same on
both VLT nodes. VLT V6 VLAN and neighbor discovery protocol monitor (NDPM) entries synchronization between VLT nodes is
performed.
The VLT V6 VLAN information must synchronize with peer VLT node. Therefore, both the VLT nodes are aware of the VLT
VLAN information associated with the peers. The CLI configuration and dynamic state changes of VLT V6 VLANs are notified to
peer VLT node. The ND entries are generally learned by a node from Neighbor advertisements (NA).
ND entries synchronization scenarios:
Virtual Link Trunking (VLT)
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