Active-Standby Lag Operation; Figure 24: Active-Standby Lag Operation Without Deployment Examples - Alcatel-Lucent 7750 Configuration Manual

Active-Standby LAG Operation

Active-Standby LAG Operation
Active/standby LAG is used to provide redundancy by logically dividing LAG into subgroups.
The LAG is divided into subgroups by either assigning each LAG's ports to an explicit subgroup
(1 by default), or by automatically grouping all LAG's ports residing on the same line card into a
unique sub-group (auto-iom) or by automatically grouping all LAG's ports residing on the same
MDA into a unique sub-group (auto-mda). When a LAG is divided into sub-groups, only a single
sub-group is elected as active. Which sub-group is selected depends on selection criterion chosen.
The active/standby decision for LAG member links is a local decision driven by pre-configured
selection-criteria. When LACP is configured, this decision was communicated to remote system
using LACP signalling.
To allow non-LACP operation, an operator must disable LACP on a given LAG and select
transmitter-driven standby signaling (configure lag standby-signaling power-off). As a
consequence, the transmit laser will be switched off for all LAG members in standby mode. On
switch over (active-links failed) the laser will be switched on all standby LAG members so they
can become active.
When the power-off is selected as the standby-signaling, the selection-criteria best-port can be
used.
It will not be possible to have an active LACP in power-off mode before the correct selection
criteria is selected.
LAG

Figure 24: Active-Standby LAG Operation without Deployment Examples

Figure 24
using sub-groups with auto-iom sub-group selection. LAG links are divided into two sub-groups
(one per line card).
In case of a link failure,
members connected to the same IOM as failing link will become stand-by and lag-members
Page 112
MC-LAG
depicts how LAG in Active/Standby mode can be deployed towards a DSLAM access
Figure 25 and Figure 26, the switch over behavior ensures that all lag-
7750 SR Interface Configuration Guide
MC-LAG MC-LAG