Users Guide

Configure Virtual Link Trunking
VLT requires that you enable the feature and then configure the same VLT domain, backup link, and VLT
interconnect on both peer switches.
Important Points to Remember
• VLT port channel interfaces must be switch ports.
• Dell Networking strongly recommends that the VLTi (VLT interconnect) be a static LAG and that you
disable LACP on the VLTi.
• If the lacp-ungroup feature is not supported on the ToR, reboot the VLT peers one at a time. After
rebooting, verify that VLTi (ICL) is active before attempting DHCP connectivity.
Configuration Notes
When you configure VLT, the following conditions apply.
• VLT domain
– A VLT domain supports two chassis members, which appear as a single logical device to network
access devices connected to VLT ports through a port channel.
– A VLT domain consists of the two core chassis, the interconnect trunk, backup link, and the LAG
members connected to attached devices.
– Each VLT domain has a unique MAC address that you create or VLT creates automatically.
– ARP tables are synchronized between the VLT peer nodes.
– VLT peer switches operate as separate chassis with independent control and data planes for
devices attached on non-VLT ports.
– One chassis in the VLT domain is assigned a primary role; the other chassis takes the secondary
role. The primary and secondary roles are required for scenarios when connectivity between the
chassis is lost. VLT assigns the primary chassis role according to the lowest MAC address. You can
configure the primary role.
– In a VLT domain, the peer switches must run the same Dell Networking OS software version.
– Separately configure each VLT peer switch with the same VLT domain ID and the VLT version. If
the system detects mismatches between VLT peer switches in the VLT domain ID or VLT version,
the VLT Interconnect (VLTi) does not activate. To find the reason for the VLTi being down, use the
show vlt statistics command to verify that there are mismatch errors, then use the show
vlt brief
command on each VLT peer to view the VLT version on the peer switch. If the VLT
version is more than one release different from the current version in use, the VLTi does not
activate.
– The chassis members in a VLT domain support connection to orphan hosts and switches that are
not connected to both switches in the VLT core.
• VLT interconnect (VLTi)
– The VLT interconnect supports a maximum of two 10G ports.
– In VLT mode, port 33 and 37 are dedicated to VLT interconnect ports.
– A VLT interconnect over 1G ports is not supported.
– The port channel must be in Default mode (not Switchport mode) to have VLTi recognize it.
– The system automatically includes the required VLANs in VLTi. You do not need to manually select
VLANs.
– VLT peer switches operate as separate chassis with independent control and data planes for
devices attached to non-VLT ports.
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PMUX Mode of the IO Aggregator