confusion about multicast load splitting

From: Michael Zuo (mzuo@ixiacom.com)
Date: Thu Mar 22 2007 - 02:03:27 ART


Hi Group,

I notice that in Cisco IOS 12.4 Documentation

http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/hi

mc_c/mcbsplit.htm#wp1066615 , it says that

the ip multicast multipath command is configured and multiple equal-cost

paths exist, the path in which multicast traffic will travel is selected

based on the source IP address

but later on it also says the selection of the interface depends on the

switching mode:

* With fast switching, load splitting occurs on a per-flow basis. A flow

is a group of packets (traffic) with the same source and destination.

Once the cache is populated for the (S, G) pair, that flow is pinned to

the physical interface assigned on the cache (the outgoing interface

used by the first packet of the flow). If the cached interface goes

down, the cache entry for the (S, G) pair is torn down and the flow is

automatically switched to a different physical interface.

*With process switching, load splitting occurs on a per-packet basis by

round-robin on the equal-cost links.

This is kind of confusing, if the load splitting is based on source IP,

how can it be using per flow/round robin at the same time?

Hope someone knows the answer to this one....

thanks



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