Working Of Ipv6 Peer Routing; Synchronization Of Ipv6 Nd Entries In A Vlt Domain; Synchronization Of Ipv6 Nd Entries In A Non-Vlt Domain - Dell S4048–ON Configuration Manual

Peer routing for IPv6 packets in a VLT domain is supported. This mechanism of 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 the control traffic to correct VLT node when the control traffic reaches 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 the neighbor entries learned on VLT VLAN interfaces between VLT 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 by 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 enables you to
replace VRRP with routed VLT to route the traffic from Layer 2 access nodes. With neighbor discovery (ND) synchronization, both
the VLT nodes will 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.

Working of IPv6 Peer Routing

When peer routing is enabled 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. This section contains the following topics that describe the
operations and benefits of IPv6 peer routing in VLT domains:

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
the VLT nodes. VLT V6 VLAN and neighbor discovery protocol monitor (NDPM) entries synchronization between VLT nodes is
performed.
The VLT-v6 VLAN information needs to be synchronized 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 should be
happening on the following two scenarios:
When VLT has been configured and enabled on both VLT node1 and node2, any dynamically learned ND entry in VLT node1 should be
synchronized instantaneously to VLT node2 and vice-versa. The link-local address will also be synchronized if learned on VLT VLAN
interface
During failure cases, when a VLT node goes down and comes back up all the ND entries learned via VLT interface must be
synchronized to the peer VLT node

Synchronization of IPv6 ND Entries in a Non-VLT Domain

L3 VLT provides a higher resiliency at the Layer 3 forwarding level. Routed VLT enables you to replace VRRP with routed VLT to
route the traffic from L2 access nodes. With ND synchronization, both the VLT nodes perform Layer 3 forwarding on behalf of each
other. Synchronization of NDPM entries learned on non-VLT interfaces between the non-VLT nodes.
In the present design the NDPM entries learned on non-VLT interfaces are synchronized with the peer VLT nodes in case the ND
entries are learned on spanned VLANs so that each node can do L3 forwarding on behalf of each other. Whenever a VLAN is
configured on VLT node, this information is communicated to the peer VLT node regardless of whether the VLAN configured is a VLT
or a non-VLT interface. If the VLAN operational state (OSTATE) is up, dynamically learned ND entry in VLT node1 is synchronized to
VLT node2.
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Virtual Link Trunking (VLT)