Reference Guide

298 | Virtual Link Trunking (VLT)
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Non-VLT ARP Sync
Prior to FTOS Version 9.2.(0.0), only ARP entries learned on VLT interfaces were synced between peers.
Now, ARP entries (including ND entries) learned on other interfaces are synced with the VLT peer.
Additionally, ARP entries resulting from station movements from VLT to non-VLT ports or to different
non-VLT ports are learned on the non-VLT port and synced with the peer node. The peer node is updated
to use the new non-VLT port.
NOTE: ARP entries learned on non-VLT, non-spanned VLANs are not synced with VLT peers.
RSTP Configuration
The RSTP Spanning Tree protocol is supported in a VLT domain. Before you configure VLT on peer
switches, you must configure the Rapid Spanning Tree Protocol (RSTP) in the network if it will be
included in your configuration. RSTP is required for initial loop prevention during the VLT startup phase.
RSTP may also be used for loop prevention in the network outside of the VLT port channel. For
information on how to configure RSTP, see Chapter 27, Rapid Spanning Tree Protocol (RSTP).
RSTP must be running on both VLT peer switches. The primary VLT peer controls RSTP states, such as
forwarding and blocking, on both the primary and secondary peers. It is recommended that you configure
the primary VLT peer as the RSTP primary root device and configure the secondary VLT peer as the RSTP
secondary root device.
BPDUs use the MAC address of the primary VLT peer as the RSTP bridge ID in the designated bridge ID
field. The primary VLT peer sends these BPDUs on VLT interfaces connected to access devices. The
MAC address for a VLT domain is automatically selected on the peer switches when you create the
domain.
3 Configure the multicast peer-routing timeout.
multicast
peer-routing—
timeout value
value:
Specify a
value (in seconds)
from 1 to 65535.
VLT DOMAIN
4 Configure a PIM-SM compatible VLT node as a designated router (DR). For more information, refer to
Configure a Designated Router.
5 Configure a PIM-enabled peer router as a rendezvous point (RP). For more information, refer to Configure
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.
Step Task
Command
Syntax Command Mode