Dell SmartFabric OS10 User Guide Release 10.5.3

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Uplink failure detection on VLT

When you create uplink-state group in a switch operating in VLT mode, ensure that all the nodes in the VLT setup have same configuration for uplink state groups with VLT port-channel as member. If both the VLT peers do not have the same UFD configuration, the UFD does not work properly.

When you configure VLT port-channel as upstream member in the uplink state group and configure to track the VLT status, the system tracks the fabric Status of VLT. When the fabric status goes down, the uplink state group in each VLT node disables the downstream VLT port-channel local to the node.

When you configure to track the VLT status, the system places the downstream members of the Uplink State Group in error disabled state or clears them from the error disabled state based on the operational status of the VLT port-channel.

When you do not track the VLT status, the system tracks the operational status of port-channel.

Track the VLT status using the upstream interface-type track-vlt-status command in UPLINK-STATE-GROUP mode.

To configure VLTi link as member of Uplink State Group, use the upstream VLTi command in UPLINK-STATE-GROUP mode. You cannot configure VLTi Link as downstream member in an uplink-state group as UFD may disable the VLTi Link when the upstream members are operationally down. You cannot track the VLT status for an upstream VLTi member.

The following table describes various scenarios when you apply UFD on a VLT network:

Table 1. UFD on VLT networkUFD on VLT network
Event	VLT action on primary node	VLT action on secondary node	UFD action
VLTi Link is operationally down with heartbeat up	No action	VLT module sends VLT port-channel disable request to Interface Manager (IFM) for both uplink and downlink.	UFD receives operationally down of upstream VLT port-channel and sends error-disable of downstream VLT port-channel to IFM.
VLTi Link is operationally up with heartbeat up	No action	VLT module sends VLT port-channel enable request to Interface Manager (IFM) for both uplink and downlink.	UFD receives operationally up of upstream VLT port-channel and sends clear error-disable of downstream VLT port-channel to IFM.
Reboot of VLT secondary peer	No action	After reboot, runs the delay restore timer. Both the upstream and downstream VLT port-channel remains disabled until the timer expires.	UFD error-disables the downstream VLT port-channel as the upstream VLT port-channel is operationally down. After the timer expires, UFD receives operationally up of upstream VLT port-channel and sends clear error-disable of downstream VLT port-channel to IFM.
Reboot of VLT primary peer	Primary becomes secondary peer and runs delay restore timer	Secondary becomes primary	UFD error-disables the downstream VLT port-channel as the upstream VLT port-channel is operationally down. After the timer expires, UFD receives operationally up of upstream VLT port-channel and sends clear error-disable of downstream VLT port-channel to IFM.
Discovery interface added to UFD group	Invalid configuration	Invalid configuration	Invalid configuration
UFD group member configured as discovery interface	Invalid configuration	Invalid configuration	Invalid configuration
UFD group member made as VLT port-channel	No action	No action	UFD uses fabric status to track the UFD group status.
VLT port-channel added as member of UFD group	No action	No action	UFD uses fabric status to track the UFD group status.
VLT port-channel configuration removed from the port-channel interface which is upstream member of UFD group	No action	No action	Stops tracking the fabric status for the UFD group. Starts tracking the local port-channel operational status, which is upstream member of the UFD group.
Fabric Status is operationally up	No action	No action	Enables the downstream members, that is clears the error-disabled state.
Fabric Status is operationally down	No action	No action	Disables the downstream members, that is sets the error-disabled state.