[c-nsp] Load-sharing between two routing protocols with same administrative distance?

[Christian Meutes]

Hi,

--On Friday, 14. November 2008 11:57 -0800 bill fumerola <billf at mu.org> 
wrote:

> redistribute routes from one protocol into another and use route-maps
> to change the metrics and route 'type' (protocol dependent) such that
> the protocol considers them equal cost.
>
> the usual warnings about route redistribution apply: using tags so loops
> don't occur and taking care not to redistribute too many routes.

wont work in most cases. Routes redistributed from IGP to BGP are better
than routes learned from eBGP or iBGP - vice versa routes redistributed
from BGP to IGP (OSPF, EIGRP ie.) are seen as external and will loose in
route decission if the IGP prefix is native/internal (will work if route is 
first learned with IGP because local redistributed routes in BGP are 
better).

In the second case you can change metric and metric-type on redistribution 
to IGP and ecmp could take place then but if the prefix is first learned 
from BGP and then from IGP - BGP wins and the OSPF prefix can't be used for 
load-sharing inside of the ASBR.

Route selection in these cases is higly depending on timeing and is 
something I wouldnt recommend.


Cheers,
christian