On Cumulus Linux, LACP Bypass is a feature that allows a bond configured in 802.3ad mode to become active and forward traffic even when there is no LACP partner. A typical use case for this feature is to enable a host, without the capability to run LACP, to PXE boot while connected to a switch on a bond configured in 802.3ad mode. Once the pre-boot process finishes and the host is capable of running LACP, the normal 802.3ad link aggregation operation takes over.
LACP Bypass All-active Mode
When a bond has multiple slave interfaces, each bond slave interface operates as an active link while the bond is in bypass mode. This is known as all-active mode. This is useful during PXE boot of a server with multiple NICs, when the user cannot determine beforehand which port needs to be active.
Keep in the mind the following caveats with all-active mode:
- All-active mode is not supported on bonds that are not specified as bridge ports on the switch.
- Spanning tree protocol (STP) does not run on the individual bond slave interfaces when the LACP bond is in all-active mode. Therefore, only use all-active mode on host-facing LACP bonds. Cumulus Networks highly recommends you configure STP BPDU guard along with all-active mode.
The following features are not supported:
- priority mode
In an MLAG deployment where bond slaves of a host are connected to two switches and the bond is in all-active mode, all the slaves of bond are active on both the primary and secondary MLAG nodes.
Configure LACP Bypass
To enable LACP bypass on the host-facing bond, set
bond-lacp-bypass-allow to yes.
You can check the status of the configuration by running
net show interface <bond> on the bond and its slave interfaces:
cat command to verify that LACP bypass is enabled on a bond and its slave interfaces:
The following configuration shows LACP bypass enabled for multiple active interfaces (all-active mode) with a bridge in traditional bridge mode: