White Papers

Table Of Contents
The IP address of the VLT node VLAN interface is synchronized with the VLT peer over ICL when the VLT peers are
up. Whenever an IP address is added or deleted, this updated information is synchronized with the VLT peer. IP address
synchronization occurs regardless of the VLAN administrative state. IP address addition and deletion serve as the trigger events
for synchronization. When a VLAN state is down, the VLT peer might perform a proxy ARP operation for the IP addresses of
that VLAN interface.
VLT nodes start performing Proxy ARP when the ICL link goes down. When the VLT peer comes up, proxy ARP will be stopped
for the peer VLT IP addresses. When the peer node is rebooted, the IP address synchronized with the peer is not flushed. Peer
down events cause the proxy ARP to commence.
When a VLT node detects peer up, it will not perform proxy ARP for the peer IP addresses. IP address synchronization occurs
again between the VLT peers.
Proxy ARP is enabled only if peer routing is enabled on both the VLT peers. If you disable peer routing by using the no
peer-routingcommand in VLT DOMAIN node, a notification is sent to the VLT peer to disable the proxy ARP. If peer routing
is disabled when ICL link is down, a notification is not sent to the VLT peer and in such a case, the VLT peer does not disable the
proxy ARP operation.
When the VLT domain is removed on one of the VLT nodes, the peer routing configuration removal will be notified to the peer.
In this case VLT peer node disables the proxy ARP. When the ICL link is removed on one of the VLT nodes by using the no
peer-link command, the ICL down event is triggered on the other VLT node, which in turn starts the proxy ARP application.
The VLT node, where the ICL link is deleted, flushes the peer IP addresses and does not perform proxy ARP for the additional
LAG hashed ARP requests.
Configuring VLAN-Stack over VLT
To configure VLAN-stack over VLT, follow these steps.
1. Configure the VLT LAG as VLAN-stack access or trunk mode on both the peers.
INTERFACE PORT-CHANNEL mode
vlan-stack {access | trunk}
2. Configure VLAN as VLAN-stack compatible on both the peers.
INTERFACE VLAN mode
vlan-stack compatible
3. Add the VLT LAG as a member to the VLAN-stack on both the peers.
INTERFACE VLAN mode
member port-channel portchannel ID
4. Verify the VLAN-stack configurations.
EXEC Privilege
show running-config
Sample configuration of VLAN-stack over VLT (Peer 1)
Configure VLT domain
Dell(conf)#vlt domain 1
Dell(conf-vlt-domain)#peer-link port-channel 1
Dell(conf-vlt-domain)#back-up destination 10.16.151.116
Dell(conf-vlt-domain)#primary-priority 100
Dell(conf-vlt-domain)#system-mac mac-address 00:00:00:11:11:11
Dell(conf-vlt-domain)#unit-id 0
Dell(conf-vlt-domain)#
Dell#show running-config vlt
!
vlt domain 1
peer-link port-channel 1
back-up destination 10.16.151.116
primary-priority 100
system-mac mac-address 00:00:00:11:11:11
unit-id 0
Dell#
Virtual Link Trunking (VLT)
881