[j-nsp] Building custom route tables from VRF's

[Gordon Smith]

> 
> Your description is not clear to me...
> 
> what do you mean by A - B "routes" ? route is a rather ambiguous term.
> 
> Do you mean that if for a given prefix you have a path from A 
> and a path from B, you want this not to be included ?
> 
> e.g. if in a table you have....
> 
>      10.0.1/24 via {A, B}
>      10.0.2/24 via A
>      10.0.3/24 via B
> 
> do you mean that you want only the second prefix ? or is it 
> something else ?
> 
> If you want to get the 2nd prefix in the example above, what 
> is the path that you prefer in the original table ? A or B... ?
> 
> if in the original table you prefer A, then you can import 
> this to another table via a rib-group where you modify the 
> local-pref such that B is preferred. Make this a VRF and in 
> its VRF export policy reject path that where received via B.
> 
> i.e. only active routes are exported from a VRF... this is a 
> way to acomplish your (A - B) logic... if i understood what you mean.
> 


Hi Pedro,

What I'm trying to achieve is what you had i.e.
I learn these routes via BGP:

10.0.1/24 via {A, B}
10.0.2/24 via A
10.0.3/24 via B

And what I want to do is take the routes learned from peer A, subtract
the routes learned from peer B, then export to a new inet table.

I've seen some examples on using community-based filters, but that does
seem like overkill for what I'm trying to achieve.
I could do it if I could dynamically construct a route-filter from one
table and apply it against the second, but I don't think that's
possible.

Both peers are in virtual-router VRF's at the moment.