Link Aggregation Minimum Active Links

The LAG Minimum Links feature allows you to configure a value for the minimum number of active links to keep the entire LAG up. For example, for a LAG consisting of 4 ports and the minimum links set to 2, at least 2 links must be up for the LAG to be up. When the LAG falls below 2 active links, the entire LAG is brought down, and all applications using this LAG will be informed that the LAG is down. Currently, the implicit minimum link value is 1, which means if there is at least 1 link up the entire LAG will stay up.

To configure this ability, use the configure sharing port minimum-active min_links_active command.

Both static and LACP LAGs are supported. In the case of static LAG, we check if the number of active physical member port links is greater than or equal to the user-configured minimum link value. If so, the LAG remains up. If the number of active physical member port links falls below the configured minimum link value, the static LAG is brought DOWN and all applications receive a Link-Down message for this LAG. As soon as the number of Active physical member ports equals or exceed the configured minimum link value, the static LAG is brought UP and all applications receive a Link-Up message for this LAG.

In the case of LACP, we keep track of the how many member ports LACP has requested to be added to the LAG. After successfully negotiating with its peer, LACP will send a request to add a member port to the LAG. When the number of member ports LACP has requested to be added to the LAG drops below the configured minimum link value, the LACP LAG will be brought down and all applications will receive a Link-Down message for this LAG. As soon LACP has added enough member ports such that the total member ports equals or exceed the configured minimum link value, the LAG is brought up and all applications receive a Link-Up message for this LAG.

Both static and LACP LAGs can be used with MLAG on either the ISC or the MLAG ports. We will verify that the minimum links feature behaves properly for static and LACP LAGs used by MLAG.

Note

For static LAGs, ensure that both ends of the LAG use the same value for minimum links. If the minimum links value differs, one side may see the LAG as down, where the other side may see the LAG as up.