[c-nsp] CEF and OSPF Q ?

[Oliver Boehmer (oboehmer)]

> I have a Q which is CEF and OSPF routing related and trying to
> understand how it works.Let us assume a router has 2 links a 256 and a
> 512Kbps links to a remote destination from the router.
> 
> So if i modify the cost of 256 and/or 512Kbps path link such that they
> look same, so that OSPF does equal cost load balancing.
> 
> My Q is how does CEF treat this and do the load balancing ? Also how
> does CEF interact with such load balancing scenarios. Are there any
> docs or URLs which would give more info.

CEF is a forwarding plane component and it picks up whatever info the
routing protocols (OSPF in this case) put into the Routing Table (RIB).
So if OSPF installs two equal cost paths, CEF will load-balance more or
less equally over these paths. If EIGRP or MPLS-TE installs unequal-cost
paths, CEF will balance the traffic accordingly (some caveats apply). 

Take a look at http://www.cisco.com/warp/public/105/46.html (general)
and http://www.cisco.com/warp/public/105/loadbal_cef.html or
http://www.cisco.com/en/US/products/hw/modules/ps2033/prod_technical_ref
erence09186a00800afeb7.html for CEF.

	oli