Service Manual

NUM Status Description Q Ports
50 Active M Po10(Gi 1/8)
M Po20(Gi 1/20)
V Po1(Gi 1/30-32)
Dell#
IPv6 Peer Routing in VLT Domains Overview
Peer routing for IPv6 packets in VLT domains is supported on the S4810, S4820T, S6000, Z9000, and MXL platforms.
Virtual Link Trunking (VLT) is a mechanism that 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.
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 trac to correct VLT node when the control trac reaches wrong VLT node due to hashing at the VLT
LAG level on the ToR.
• Routing the data trac 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 congured time period when a peer VLT node goes down.
When you congure Layer 3 VLT peer routing by using the peer-routing command in VLT DOMAIN mode, it applies for both IPv4 and
IPv6 trac 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 trac 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 trac 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 benets 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 conguration and dynamic state changes of VLT v6 VLANs are notied 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 congured 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
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Virtual Link Trunking (VLT)