Service Manual

Table Of Contents
If NA is intended for VLT peer and DIP is LLA of peer, it is lifted to CPU and tunneled to the peer. VLT
nodes will drop NA packet, If NA is received over ICL without tunneling header.
Neighbor Solicitation from Non-VLT Hosts
Consider a sample scenario in which NS for VLT node1 IP reaches VLT node1 on non-VLT interface and
NS for VLT node1 IP reaches VLT node2 on non-VLT interface. When VLT node1 receives NS from non-
VLT interface, it unicasts NA packet on the received interface. When NS reaches VLT node2 it is VLAN
flooded on all interfaces including ICL. When VLT node 1 receives NS on ICL then it floods NA packet on
the VLAN. If NS is unicast and if reaches wrong VLT peer it is lifted to CPU using ACL entry. Then wrong
peer adds tunnel header and forwards the packet over ICL
Neighbor Advertisement from Non-VLT Hosts
Consider a situation in which NA for VLT node1 reaches VLT node1 on non-VLT interface and NA for VLT
node1 reaches VLT node2 on non-VLT interface. When VLT node1 receives NA on VLT interface, it learns
the Host MAC address on received interface. This learned neighbor entry is synchronized to VLT node2 as
it is learned on ICL. If VLT node2 receives a NA packet on non-VLT interface which is destined to VLT
node1, node 2 will lift the NA packet to CPU using an ACL entry then it adds a tunnel header to the
received NA and forwards the packet to VLT node1 over ICL. When VLT node1 received NA over ICL with
tunnel header it learns the Host MAC address on ICL. Host entries learned on ICL will not be
synchronized to the VLT peer.
If NA is intended for VLT peer and DIP is LLA of peer, it is lifted to CPU and tunneled to the peer. VLT
nodes will drop NA packet, If NA is received over ICL without tunneling header.
Traffic Destined to VLT Nodes
Hosts can send traffic to one of the VLT nodes using global IP or Link-Local address. When host
communicates with VLT node using LLA and traffic reaches wrong peer due to LAG level hashing in TOR,
the wrong peer should route the packet to correct VLT node though the destination IP is LLA. Consider a
case in which traffic destined for VLT node1 reaches VLT node1 on VLT interface and traffic destined for
VLT node1 reaches VLT node2 due to LAG level hashing in TOR.
When VLT node1 receives traffic on VLT interface, it consumes the packets and process it based on the
packet type. If VLT node2 receives packet on VLT interface which is destined to VLT node1, it routes the
packet to VLT node1 instead of switching the packet owing to the match that occurs for the neighbor
entry in the TCAM table.
If the destination IP address is peers' link-local advertisement (LLA), wrong VLT peer will switch the traffic
over ICL. This is achieved using switching egress object for peers LLA.
VLT host to North Bound traffic flow
One of the VLT peer is configured as default gateway router on VLT hosts. If VLT node receives L3 traffic
intended for the other VLT peer it routes the traffic to next hop instead of forwarding the traffic to the
VLT peer. If neighbor entry is not present VLT node will resolve the next hop. There may be traffic loss
during neighbor resolution period.
North-Bound to VLT host traffic flow
Virtual Link Trunking (VLT)
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