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RE: OSPF unequal cost load balancing posted 05/23/2001
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Follow up, quoted from RFC 2328:

"The OSPF protocol maintains multiple equal-cost routes to all destinations.
This can be seen in the steps used above to calculate the routing table, and
in the definition of the routing table structure.

" Each one of the multiple routes will be of the same type (intra-area,
inter-area, type 1 external or type 2 external), cost, and will have the
same associated area. However, each route may specify a separate next hop
and Advertising router.

"There is no requirement that a router running OSPF keep track of all
possible equal-cost routes to a destination. An implementation may choose to
keep only a fixed number of routes to any given destination. This does not
affect any of the algorithms presented in this specification. "

So Cisco appears to have decided that 4 is the magic number. There may be
practical reasons for this, but according to the RFC, there could be more or
fewer equal cost paths supported.

But no, OSPF does not support unequal cost paths, which would defeat the
purpose of the algorithm in the first place.



-----Original Message-----
From:	nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On Behalf Of
Shane Miles
Sent:	Wednesday, May 23, 2001 11:25 AM
To:	'ccielab@xxxxxxxxxxxxxx'
Subject:	OSPF unequal cost load balancing

	My understanding is that when using OSPF you can have up to 4
equal-cost paths performing load balancing.  Is it at all possible to do
unequal cost load balancing with OSPF as is possible with EIGRP?

Shane P. Miles
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