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Port Channel Commands 611
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Port Channel Commands
A port channel is a set of one or more links that can be aggregated together to
form a bonded channel (Link Aggregation Group or LAG). Individual
conversations in a particular direction always travel over a single link in the
port channel, however, in aggregate, the bandwidth usage of all of the links is
fairly evenly distributed. Port channels have the advantage of allowing
incremental bandwidth to be added as needed (by adding additional links)
and supporting a form of fault tolerance (traffic on failed links is redistributed
among other links in the LAG). LAGs are formed from similarly configured
physical links, i.e. the speed, duplex, auto-negotiation, PFC configuration,
DCBX configuration, etc. must be identical on all member links.
Care must be taken while enabling this type of configuration. If the Partner
System is not 802.3AD compliant or the Link Aggregation Control protocol is
not enabled, there may be network instability. Network instability occurs
when one side assumes that the members in an aggregation are one single
link, while the other side is oblivious to this aggregation and continues to
treat the 'members' as individual links.
In the PowerConnect system, the Actor System waits for 3 seconds before
aggregating manually. The 3 second wait time is specified by the protocol
standard.
If a manual LAG member sees an LACPDU that contains information
different from the currently configured default partner values, that particular
member drops out of the LAG. This configured member does not aggregate
with the LAG until all the other active members see the new information.
When each of the other active members sees the new information, they
continue to drop out of the LAG. When all the members have dropped out of
the LAG, they form an aggregate with the new information.
Static LAGS
A static LAG is fundamentally no different from a dynamically configured
LAG. All the requirements for the member ports hold true (member ports
must be physical, same speed, and so on). The only difference is this LAG has
2CSPC4.X8100-SWUM102.book Page 611 Friday, March 15, 2013 8:56 AM