[j-nsp] Optimizing the FIB on MX

[Alexander Arseniev]

Hello,

On 17/02/2016 19:51, Vincent Bernat wrote:
> Hey!
>
>
> If the condition system would allow me to match a next-hop or an
> interface in addition to a route, I could do:
>
>   3. Reject any route with upstream as next-hop if there is a default
>      route to upstream.
>
>   4. Reject any route with peer as next-hop if there is a default route
>      to peer.
>
>   5. Accept everything else.

True, one cannot match on "next-hop" in "condition", only on exact 
prefix+table name.
But this can be done using "route isolation" approach.
So, the overall approach is:
1/ create a separate table and leak a 0/0 route there matching on 0/0 
exact + next-hop ("isolate the interested route"). Use "instance-import" 
+ policy.
2/ create condition

policy-options {
  condition default-to-upstream {
   if-route-exists {
    0.0.0.0/0;
    table isolate-0/0.inet.0;
   }
  }

3/ use condition to match & reject the specifics:

policy-options {
  policy-statement reject-same-nh-as-0/0 {
   term 1  {
               from {
                 protocol bgp;
                route-filter 0/0 longer;
                 condition default-to-upstream;
		next-hop 198.18.1.1;
             }
             then reject;
         }
  term 2  {
               from {
                 protocol bgp;
                route-filter 0/0 longer;
		next-hop 198.18.1.1;
             }
             then accept;
         }

Disclaimer - I haven't tested this myself.

HTH
Thx
Alex