Nokia 7705 SAR - 3.2.13.7 Static LAG (Active;Standby LAG Operation without LACP)

Interface Configuration Guide 7705 SAR Interfaces
Edition: 01 3HE 11011 AAAC TQZZA 113
3.2.13.7 Static LAG (Active/Standby LAG Operation without LACP)
Some Layer 2 capable network equipment devices support LAG protected links in an
active/standby mode but without LACP. This is commonly referred to as static LAG.
In order to interwork with these products, the 7705 SAR supports configuring LAG
without LACP.
LACP provides a standard means of communicating health and status information
between LAG peers. If LACP is not used, the peers must be initially configured in a
way that ensures that the ports on each end are connected and communicating.
Otherwise, LAG will not be active. Which LAG peer is made active is a local decision.
If the port priority settings are the same for all ports, it is possible that the two ends
will select ports on different physical links and LAG will not be active. Decide the
primary link by setting the port priority for the LAG on each peer to ensure that the
active ports on each end coincide with the same physical link.
The key parameters for configuring static LAG are selection-criteria (set to
best-port) and standby-signaling (set to power-off). The selection criteria is used
to determine which selection algorithm decides the primary port (the active port in a
no-fault condition). It is always the subgroup with the best-port (the highest-priority
port - lowest configured value) that is chosen as the active subgroup. The selection
criteria must be set to best-port before standby signaling can be placed in power-off
mode. Once the selection criteria is set to best-port, setting the standby-signaling
parameter to power-off causes the transmitters on the standby ports to be powered
down.
After a switchover caused by a failure on the active link, the transmitters on the
standby link are powered on. The switch time for static LAG is typically longer than it
is with LACP, due to the time it takes for the transmitters to come up and transmission
to be established. When the fault is restored, static LAG causes a revertive switch to
take place. The revertive switch is of shorter duration than the initial switchover since
the system is able to prepare the other side for the switch and initiate the switchover
once it is ready.
Note: Since the transmitters on the standby link are off, it is not possible for the LAG to
respond to a physical disconnect (fault) on the standby link. This means that it is possible
to have a failure on the active link result in a switch to a failed standby link.