Hi,

In our scenario we have 3 uplinks from 3 ISPs. We have own AS number and 8 /24 prefixes purchased from APNIC. We are accepting only default route via BGP from our Upstreams. Link X is of 310 mbps, Y of 155 mbps & Z of 60 mbps.

No we want symmetric BGP routing with failover like we want to route 5 /24 prefix over Link X // 2 /24 over Link Y // 1 /24 over Link Z but in case of failure of any link it must auto failover to another.

We are able to do the incoming traffic (Download trafic) via BGP AS Path Prepend. But I'm facing problem routing outgoing traffic which results in sometime some IP takes X path and a minute later it takes Y path and so on.

I have attached our current routing configuration.

I tried mangle-->mark route and then ip-> route // route mark and changed gateway. But not working well. Also failover is not working.

Any help is highly appreciated.

Thanks & Regards,
Srijit Banerjee.

If I get it correctly, what you want to do can be achieved by changing the LOCAL_PREF of the routes received,

But since you're just accepting default routes, all you can do is failover (how can you discern which routes you want to prioritize on certain provider when all are 0.0.0.0/0?)

Set BGP filters (on a peer basis) that change the LOCAL_PREF of received routes to something bigger than 100, for instance, if you want ISP X to be the main one, set a filter to change it to let's say 500, ISP Y is the second one, change set it to 300 and the Z ISP, don't change it since it'll use the default pref which is 100.

This way you'll achieve fail-over

Hello,

I believe you can achieve this with traditional policy routing.

Use firewall mangle rules to mark packets/connections when they enter your router coming from your networks.
Then use these routing marks with routes received from your upstreams.

Lab it first though

By the way, if you advertise all your prefixes to all your upstreams, then you cannot be 100% sure that the traffic from one /24 is coming through the "correct" upstream, even with prepend.

Are you using only BGP learned default routes or are you taking in full tables as well?

Are you using only BGP learned default routes or are you taking in full tables as well?

As he said, he's receiving only default routes from his ISPs.

The best way to solve this is to get a big enough router (eg RB1100AHx2 or CCR1009) and take full feeds from each ISP. That's what I do, it works well if you have the right mix of ISPs.