ISP BGP goes down, stops advertising a default route to us. How to stop originating a route via ospf default originate

[patricianet]

Our ISP is sending us a default route.

We are also originating a default route into our network via ospf default information originate.

The problem we are running into is that when we lose our ISP, but we do not lose our peering, we no longer receive the default route but ospf is still originating a defualt route and since the default route is in the routing table BGP sends traffic to our ISP, blackholing our traffic. How do I force BGP to stop advertising the default route. I was thinking to use an exist or non exist map but that will not work since the route will be in the routering table via ospf default information originate. 

Any suggestions?

[Jon Marshall]

A bit of clarification is needed.

If you use under your ospf config -

ospf default-information originate

then OSPF will only advertise a default-route if there is on in the routing table.

If you use -

opsf default-information originate always

then OSPF will advertise a default-route regardless of whether there is a default-route in the routing table.

You say -

we no longer receive the default route but ospf is still originating a defualt route and since the default route is in the routing table BGP

there are a number of confusing things here -

1) if you no longer receive the default-route then there should not be a default-route in the routing table so OSPF should stop advertising

2) you say you no longer receive the default-route but then say it is still in BGP routing table. How can it be if you no longer receive it ?

Jon