Service Manual

Consider a case in which NS for VLT node1 IP reaches VLT node1 on VLT interface and NS for VLT node1 IP reaches VLT node2 due
to LAG level hashing in TOR. When VLT node1 receives NS from VLT VLAN interface, it unicasts NA packet on the VLT interface.
When NS reaches VLT node2 it is ooded on all interfaces including ICL. When VLT node 1 receives NS on ICL then it oods 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 VLT Hosts
Consider an example in which NA for VLT node1 reaches VLT node1 on VLT interface and NA for VLT node1 reaches VLT node2 due
to LAG level hashing in TOR. When VLT node1 receives NA on VLT interface, it learns the Host MAC address on VLT interface. This
learned neighbor entry is synchronized to VLT node2 as it is learned on VLT interface of Node2. If VLT node2 receives a NA packet
on 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 receives NA over ICL with tunnel
header it learns the Host MAC address on VLT port channel interface. This learned neighbor entry is synchronized to VLT node2 as it
is learned on VLT interface of Node2.
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 ooded on all interfaces including ICL. When VLT node 1 receives NS on ICL then
it oods 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.
Trac Destined to VLT Nodes
Hosts can send trac to one of the VLT nodes using global IP or Link-Local address. When host communicates with VLT node using
LLA and trac 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 trac destined for VLT node1 reaches VLT node1 on VLT interface and
trac destined for VLT node1 reaches VLT node2 due to LAG level hashing in TOR.
When VLT node1 receives trac 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 trac over ICL. This is achieved
using switching egress object for peers LLA.
VLT host to North Bound trac ow
Virtual Link Trunking (VLT)
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