Reference Guide

NA messages can be sent in two types of scenarios:
• Sometimes NA messages are sent by a node when its link-layer address is changed. This NA message
is sent as an unsolicited NA to advertise its new address and the destination address field is set to the
link-local scope of all-nodes multicast address. This unsolicited NA packet need not be tunneled.
• NA messages are almost always sent in response to an NS message from a node. In this case the
solicited NA has the destination address field set to the unicast MAC address of the initial NS sender.
This solicited NA need to be tunneled when they reach the wrong peer.
Consider a sample scenario in which two VLT nodes, Unit1 and Unit2, are connected in a VLT domain
using an ICL or VLTi link. To the south of the VLT domain, Unit1 and Unit2 are connected to a ToR switch
named Node B. Also, Unit1 is connected to another node, Node A, and Unit2 is linked to a node, Node C.
When an NS traverses from Unit2 to Node B(TOR) and a corresponding NA reaches Unit1 because of LAG
hashing , this NA must be tunneled to Unit 2 along with some control information. The control
information present in the tunneled NA packet is processed in such a way that the ingress port is marked
as the link from Node B to Unit 2 rather than pointing to ICL link through which tunneled NA arrived.
Sample Configuration of IPv6 Peer Routing in a VLT Domain
Consider a sample scenario as shown in the following figure in which two VLT nodes, Unit1 and Unit2, are
connected in a VLT domain using an ICL or VLTi link. To the south of the VLT domain, UNit1 and Unit2
are connected to a ToR switch named Node B. Also, Unit1 is connected to another node, Node A, and
Unit2 is linked to a node, Node C. The network between TOR to VLT Nodes is purely L2 in nature. Servers
or hosts that are connected to the ToR (Node B) generate the L3 control/data traffic from the South or
lower-end of the vertically-aligned network.
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Virtual Link Trunking (VLT)