Addendum

When using factory default settings on a new switch deployed as a VLT node, packet loss may occur
due to the requirement that all ports must be open.
ECMP is not compatible on VLT nodes using VLT multicast. You must use a single VLAN.
Configuring VLT Multicast
To enable and configure VLT multicast, follow these steps.
1. Enable VLT on a switch, then configure a VLT domain and enter VLT-domain configuration mode.
CONFIGURATION mode
vlt domain domain-id
2. Enable peer-routing.
VLT DOMAIN mode
peer-routing
3. Configure the multicast peer-routing timeout.
VLT DOMAIN mode
multicast peer-routing—timeout value
value: Specify a value (in seconds) from 1 to 1200.
4. Configure a PIM-SM compatible VLT node as a designated router (DR). For more information, refer to
Configuring a Designated Router.
5. Configure a PIM-enabled external neighboring router as a rendezvous point (RP). For more
information, refer to
Configuring a Static Rendezvous Point.
6. Configure the VLT VLAN routing metrics to prefer VLT VLAN interfaces over non-VLT VLAN
interfaces. For more information, refer to
Classify Traffic.
7. Configure symmetrical Layer 2 and Layer 3 configurations on both VLT peers for any spanned VLAN.
Non-VLT ARP Sync
Synchronization for non-ARP routing table entries is supported on the Z9000 S4810 S4820T platform.
Prior to FTOS version 9.2.(0.0), only ARP entries learned on VLT ports were synced between peers. In
9.2(0.0), ARP entries (including ND entries) learned on other ports are synced with the VLT peer to
support station move scenarios.
NOTE: ARP entries learned on non-VLT, non-spanned VLANs are not synced with VLT peers.
Verifying a VLT Configuration
To monitor the operation or verify the configuration of a VLT domain, use any of the following show
commands on the primary and secondary VLT switches.
Display information on backup link operation.
EXEC mode
show vlt backup-link
Display general status information about VLT domains currently configured on the switch.
EXEC mode
show vlt brief
Display detailed information about the VLT-domain configuration, including local and peer port-
channel IDs, local VLT switch status, and number of active VLANs on each port channel.
EXEC mode
show vlt detail
Virtual Link Trunking (VLT)
467