LAG
Page 34 7210 SAS M, T, X, R6, R12, Mxp Interface Configu-
ration Guide
LAG
Based on the IEEE 802.3ax standard (formerly 802.3ad), Link Aggregation Groups (LAGs) can be
configured to increase the bandwidth available between two network devices, depending on the
number of links installed. LAG also provides redundancy in the event that one or more links
participating in the LAG fail. All physical links in a given LAG links combine to form one logical
interface.
Packet sequencing must be maintained for any given session. The hashing algorithm deployed by
Alcatel-Lucent routers is based on the type of traffic transported to ensure that all traffic in a flow
remains in sequence while providing effective load sharing across the links in the LAG.
LAGs must be statically configured or formed dynamically with Link Aggregation Control
Protocol (LACP). The optional marker protocol described in IEEE 802.3ax is not implemented.
LAGs can be configured on network and access ports.
LAG Features
Hardware capabilities:
• The LAG load sharing is executed in hardware, which provides line rate forwarding for all
port types.
Software capabilities:
• The Alcatel-Lucent solution conforms to the IEEE LAG implementation including
dynamic costing and LAG port threshold features. The dynamic cost and LAG port
threshold features can be enabled even if the second node is not an Alcatel-Lucent router.
→ Dynamic cost
Dynamic cost can be enabled with the config>lag dynamic-cost
command or by the
action specified in the config>lag>port-threshold command.
If dynamic cost is enabled and the number of active links is greater than the port
threshold value (0-7 or 0-15), depending on chassis-mode and IOM type), then the
path cost is dynamically calculated whenever there is a change in the number of active
links regardless of the specified port threshold action. If the port-threshold is met and
the action is set to dynamic cost, then the path cost is dynamically recalculated
regardless of the global dynamic cost configuration.
Enabling dynamic costing causes the physical link metrics used by OSPF to be
applied based on the operational or aggregate link bandwidth in the LAG that is
available at the time, providing the number of links that are up exceeds the configured
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