Reference Guide

L3 VLAN
connectivity
Enable L3 VLAN connectivity (VLANs assigned with an IP address) on VLT peers by configuring a VLAN
interface for the same VLAN on both devices.
Optimized
forwarding with
VRRP
To enable optimized L3 forwarding over VLT, use VRRP Active-Active mode. VRRP Active-Active mode
enables each peer to locally forward L3, resulting in reduced traffic flow between peers over the VLTi.
Spanning-Tree
Protocol
RSTP and RPVST+ are supported on VLT ports.
NOTE: 802.1x, DHCP snooping, MSTP, IGMP snooping, MLD snooping, ingress and egress QoS are not supported on VLT
ports.
Terminology
Discovery
interface
Port interfaces on VLT peers in the VLT interconnect (VLTi) link.
Virtual-link
trunk (VLT port-
channel)
A combined port-channel between an attached device and VLT peer switches.
VLT domain The domain includes VLT peer devices, VLT interconnect, and all port-channels in the VLT connected to
the attached devices. It is also associated with the configuration mode that you must use to assign VLT
global parameters.
VLT interconnect
(VLTi)
The link between VLT peer switches used to synchronize operating states.
VLT MAC address (Optional) Unique MAC address that you assign to the VLT domain. A VLT MAC address is the common
address used for all VLT peers. If you do not configure a VLT MAC address, the MAC address of the
primary peer is used as the VLT MAC address across all peers.
VLT peer device A pair of devices connected using a dedicated port-channel — the VLTi.
VLT port-channel
ID
Groups port-channel interfaces on VLT peers into a single virtual-link trunk connected to an attached
device. Assign the same port-channel ID to interfaces on different peers that you bundle together.
VLT Node
Priority
The priority based on which the primary and secondary VLT nodes are determined. If priority is not
configured, the VLT node with the lowest MAC address is elected as the primary VLT node.
VLT peer switches have independent management planes. A VLTi between the VLT chassis maintains synchronization of L2/L3
control planes across the two peer switches.
VLT domain
A VLT domain includes the VLT peer devices, VLT interconnect, and all port-channels in the VLT that connect to the attached
devices. It is also associated with the configuration mode that you must use to assign VLT global parameters.
● A VLT domain supports two node members. These peer devices appear as a single logical device to network access devices
that connect to VLT ports through a port-channel.
● A VLT domain consists of the two core nodes, interconnect trunk, and LAG members that connect to attached devices.
● Each VLT domain must have a unique MAC address that you create or that VLT creates automatically.
● VLAN ID 4094 is reserved as an internal control VLAN for the VLT domain.
● ARP, IPv6 neighbors, and MAC tables synchronize between the VLT peer nodes.
● VLT peer devices operate as a separate node with independent control and data planes for devices that attach to non-VLT
ports.
● One node in the VLT domain takes a primary role and the other node takes the secondary role. In a VLT domain with two
nodes, the VLT assigns the primary node role to the node with the lowest MAC address. By default, VLT assigns the primary
node role to the node with the lowest system MAC address. You can override the default primary election mechanism by
assigning priorities to each node using the primary-priority command.
● If the primary peer fails, the secondary peer (with the higher priority) takes the primary role. If the primary peer (with the
lower priority) later comes back online, it is assigned the secondary role (there is no preemption).
● In a VLT domain, the peer network devices must run the same OS10 software version.
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Virtual Link Trunking