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

[bill fumerola]

On Sat, Nov 15, 2008 at 10:09:53AM +0100, Christian Meutes 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.

any method that tries to equate two different routes from different
protocols is going to be messy and require tweaking of origins, metrics,
and/or distances(!).

i wouldn't recommend doing any of this, was just suggesting a way to do
what the OP was asking.

-- bill