Users Guide

1048 Link Aggregation
• Excellent load balancing performance.
How Do LAGs Interact with Other Features?
From a system perspective, a LAG is treated just as a physical port, with the
same configuration parameters for administrative enable/disable, spanning
tree port priority, path cost as may be for any other physical port.
VLAN
When members are added to a LAG, they are removed from all existing
VLAN membership. When members are removed from a LAG they are added
back to the VLANs that they were previously members of as per the
configuration file. Note that a port’s VLAN membership can still be
configured when it's a member of a LAG. However this configuration is only
actually applied when the port leaves the LAG.
The LAG interface can be a member of a VLAN complying with IEEE
802.1Q.
STP
Spanning tree does not maintain state for members of a LAG, but does
maintain state for the LAG interface. As far as STP is concerned, members of
a LAG do not have individual link state. (Internally, the STP state of the LAG
interface is replicated for the member links.)
When members are deleted from a LAG they become normal links, and
spanning tree maintains their individual link state information.
Statistics
Statistics are collected for LAGs in the same manner as they are collected for
the physical ports, in addition to the statistics collected for individual
members as per the 802.3ad MIB statistics.
LAG Configuration Guidelines
Ports to be aggregated must be configured so that they are compatible with
the link aggregation feature and with the partner switch to which they
connect.
Ports to be added to a LAG must meet the following requirements:
• Interface must be a physical Ethernet link.