Routing

Dear friends!

 

We need to advertise a default route to one of our bgp customers. I know a way is to use a generated route of 0.0.0.0/0 and export it neighbour via policy.

 

But in our case we already have a static defaul route towards our Core network on this Route with no-readvertise knob, due to which this exporting method is not working.

 

Can someone suggest how can i achieve this originating of default route to customer. I cannot afford to remove the default route of the Router nor can remove no-readvertise keyword.

 

Regards,

Asad

Hi Assad,

A possible solution would be to create a routing instance that includes your customer faceing interfaces. In its routing table you can have a default route that does not interfere with your route to the core.

Regards,
Dominik

Hi Asad,

 

I cannot test this right now but could you not configure an "aggregate" 0/0 router under routing-options ?

These routes are never used for forwarding (next-hop = reject) contrary to generated-routes and therefore I believe they are always active (and exportable via BGP).

 

HTH,

/david

Hi,

 

I do not think it is going to work as aggregate route would be inactive due to protocol preference 130 (static 5). Question: Why do you want to redistribute something you yourself declared as non-redistrubutable?

 

Thanks!

Michael Pergament

 

hi.... aggregatd n generated wouldn't work ... i have checked it...

 

this router of mine i s a access router .. and its connected to core network.. and we use default route on this router towards core network... adn we don'y want this router to propagate this default route in ospf so we use no re-advertise with default rote.

 

As a customer requirement we need to export default to one of our customers on this router..

Considering this I thing a separate routing instance shout fit well. Because then you can fully separate the customer routes from your internal ones, you can individual configure IGP etc.

 

Regards,

Dominik

Well, then take approach from Dominik:

lab@england# show routing-instances
test {
    instance-type virtual-router;
    interface ge-0/0/3.0;
    routing-options {
        static {
            route 0.0.0.0/0 next-table inet.0;
        }
    }
    protocols {
        bgp {
            group test {
                type internal;
                local-address 30.30.30.1;
                export test;
                neighbor 30.30.30.2;
            }
        }
    }
}

 

lab@germany# run show route

inet.0: 15 destinations, 15 routes (15 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

0.0.0.0/0          *[BGP/170] 00:13:02, localpref 100
                      AS path: I
                    > to 30.30.30.1 via ge-0/0/3.0

 

Regards

Michael

Why not create an OSPF export policy that prevents the static route from being advertised into OSPF?  The no re-advertise knob is just a second line of defense anyway - OSPF will not use it unless defined in a policy.  Explicitly rejecting the 0/0 route, with policy, should solve your OSPF problem.  A commit script for the OSPF export policy could check to ensure the default route is denied in the future.

 

Once OSPF is prevented from accepting (export policy) the default route, you will be free to advertise the 0/0 route to your BGP customer.