Dell C1048P Port Extender Networking Configuration Guide for the C9000 Series - Page 978

- 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 can configure using the system-mac command. If you do not specify a MAC address, VLT uses the primary peer's MAC address by default. - 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 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 mismatch 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 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 nonVLT ports. - Port-channel link aggregation (LAG) across the ports in the VLT interconnect is required; individual ports are not supported. Dell Networking strongly recommends configuring 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 traffic only when there is a link failure that requires using VLTi in order for data packets to reach their final destination. - Unknown, multicast, and broadcast traffic can be flooded across the VLT interconnect. - MAC addresses for VLANs configured 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 configured 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 configure 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 flap. - In a VLT domain, the following software features are supported on VLTi: link layer discovery protocol (LLDP), flow 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 configured information is true on both peer switches: * the VLT-system MAC address (if configured) matches. * the VLT unit-id (if configured) is not identical. NOTE: If the VLT-system MAC address or VLT unit-id is not configured on both VLT peer switches, VLT automatically sets the default VLT-system MAC address and unit-id on each peer. - If the link between the VLT peer switches is established, changing the VLT-system MAC address or the VLT unit-id causes the link between the VLT peer switches to become disabled. However, removing the VLT-system MAC address or the VLT unit-id may disable the VLT ports if you happen to configure the unit ID or system MAC address on only one VLT peer at any time. - If the link between VLT peer switches is established, any change to the VLT-system MAC address or unit-id fails if the changes made create a mismatch by causing the VLT unit-ID to be the same on both peers and/or the VLT-system MAC address does not match on both peers. - If you replace a VLT peer node, pre-configure the switch with the VLT-system MAC address, unit-id, and other VLT parameters (if applicable) before connecting it to the existing VLT peer switch using the VLTi connection. Virtual Link Trunking (VLT) 978