Service Manual

Conguration Notes
When you congure 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 congure the primary role.
– In a VLT domain, the peer switches must run the same Dell Networking OS software version.
– Separately congure 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 nd 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 dierent 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 must consist of either 10G or 40G ports. A maximum of eight 10G or four 40G ports is supported. A
combination of 10G and 40G ports is not supported.
– 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.
– Port-channel link aggregation (LAG) across the ports in the VLT interconnect is required; individual ports are not supported.
Dell Networking strongly recommends conguring a static LAG for VLTi.
– The VLT interconnect synchronizes L2 and L3 control-plane information across the two chassis.
– The VLT interconnect is used for data trac only when there is a link failure that requires using VLTi in order for data packets
to reach their nal destination.
– Unknown, multicast, and broadcast trac can be ooded across the VLT interconnect.
– MAC addresses for VLANs congured across VLT peer chassis are synchronized over the VLT interconnect on an egress port
such as a VLT LAG. MAC addresses are the same on both VLT peer nodes.
– ARP entries congured across the VLTi are the same on both VLT peer nodes.
– If you shut down the port channel used in the VLT interconnect on a peer switch in a VLT domain in which you did not
congure a backup link, the switch’s role displays in the show vlt brief command output as Primary instead of
Standalone.
– When you change the default VLAN ID on a VLT peer switch, the VLT interconnect may ap.
– In a VLT domain, the following software features are supported on VLTi: link layer discovery protocol (LLDP), ow control,
port monitoring, jumbo frames, and data center bridging (DCB).
– When you enable the VLTi link, the link between the VLT peer switches is established if the following congured information
is true on both peer switches:
* the VLT system MAC address matches.
* the VLT unit-id is not identical.
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Virtual Link Trunking (VLT)