# Link-State Tracking

Link-state tracking binds the link state of multiple interfaces, creating so-called link-state groups with upstream (to-be-followed) and downstream (to-follow) interfaces. The association between the upstream set and the downstream set is a link-state tracking group. If all interfaces in the upstream set have a ‘down’ operational status, all interfaces in the downstream set must be disabled also. If at least one upstream interface is considered up, the downstream interfaces are enabled.

By default, each link-state tracking group is disabled and both upstream and downstream member sets are empty.

Valid interfaces are ports and trunks (both statically defined and formed by link aggregation).

For the operational status, both the physical link state and VLACP state (if VLACP is enabled on the interface) are considered as follows:

- When VLACP is disabled on the interface, up and down correspond directly to the interface operational state (physical link). In the case of trunks, a last-link-down event triggers a down state for the corresponding group entry. Similarly, a first-link-up triggers an up state.

- If VLACP is enabled, the interface is considered up if it has link-up and VLACP partner, and down otherwise.

## Limitations

- The feature currently supports two link-state groups.

- The maximum number of upstream members is eight.

- The maximum number of downstream members is 384.

- Interfaces can belong to only one link-state group.

- An interface cannot be an upstream and downstream member simultaneously.

- You cannot add a trunk-member port to a link-state tracking group by itself.

- Only enabled trunks can be tracking group members. You cannot disable a trunk which is a tracking group member.

- You cannot add ports with link aggregation enabled to a tracking group. You cannot enable link aggregation on a tracking group member port.

- Operational states for interfaces and tracking groups are dynamically determined during switch operation and are not saved in binary/ASCII configuration.

Parent topic: Link-State Tracking fundamentals