[c-nsp] Dual-homing scenario

[Roy]

Vincent De Keyzer wrote:
> Hello,
>
>  
>
> let a dual-home BGP network. ISP1 comes in with a T3 and sends a full BGP
> table; ISP2 comes with a FE and a default-route (for memory reasons).
>
>  
>
> ISP2 is preferrable because of capacity, but ISP1 is preferred because any
> route is more specific than a default route; hence all upstream traffic goes
> to ISP1, which is not good.
>
>
>   
Several suggestions:

1) The best solution is that you ask for ISP1 to send you only their 
customer routes instead of a full table.

2) Throw away any routes from ISP1 that have more than two AS numbers

3) Throw away any routes fom ISP1 that are shorter that /16 (or some 
other number)

4) Some mix of 2 and 3

In all scenarios set a default route to ISP1 that is lower in priority 
than the one to ISP2