[j-nsp] Simulate minimum-links for ordinary interfaces?

[p1 at westerlund.se]

Hi!

I have not been able to figure out how to "disable" the remaining 
interfaces among a set of interfaces when one goes down. Is it even 
possible? I'm looking for something like "minimum-links" for LAGs.

The background is that we are using an external service that is 
filtering our outbound traffic. The connection is set up using IPsec 
tunnels. One tunnel is not enough, we have to load-balance over more 
than one to have enough total bandwidth (load-balancing is set up and 
works well).

There is one primary filtering site, and a secondary site. All traffic 
is routed to the same IPv4-address that exists in both sites.

Here is a configuration example:

ladmin at srx-1> show configuration routing-instances outbound-vr
instance-type virtual-router;
interface st0.1; # Primary site
interface st0.2; # Primary site
interface st0.3; # Secondary site
interface st0.4; # Secondary site
routing-options {
     static {
         route 1.2.3.4/32 {
             qualified-next-hop st0.1 {
                 metric 1;
             }
             qualified-next-hop st0.2 {
                 metric 1;
             }
             qualified-next-hop st0.3 {
                 metric 2;
             }
             qualified-next-hop st0.4 {
                 metric 2;
             }
         }
     }
}

If st0.1 goes down, st0.2 cannot handle all of the load, so we want to 
move all of the traffic to st0.3 and st0.4 instead. Ideally, once st0.1 
recovers, the traffic should move back to st0.1 and st0.2.

Is this possible to do in a good way?

I know that almost anything can be solved with event-scripts triggered 
by link-up/down for st0.X, but that kind of configuration is somewhat 
hidden, and also probably difficult to get completely correct.


Any hints appreciated.

/Per Westerlund