[j-nsp] External routes in OSPF database

[Harry Reynolds]

No, junos does not automatically redistribute bgp into igp by default. 

>From a quick read it sounds to me like the cisco is set to redistribute bgp into ospf (though you did say isis is the igp). That would explain why all the externals appear after ospf adjacency up. 
Perhaps due to rule of sync, which is normally disabled to avoid such a ridiculous need (that is, to require that the igp have a route before it can be advertised by BGP).

I would check the ios config for a redistribute bgp under isis or such.

Should be easy to confirm from where the externals are originating through its router-id.

Your policy below seems sufficient to advertise a default route, but it will not block any type 1, 2, 3, 4, and 5 lsas that are present (say due to a full bgp feed being leaked into the igp). If you wish *only* a default and type 1/2 lsas (and a type 3 for the default) you may consider setting as a totally stubby network (which should not be area 0):

{master}[edit]
regress at mse-a# show protocols ospf area 1 
stub default-metric 10 no-summaries;

With this config you will not need the static default as it will be auto-generated. 


HTHs




-----Original Message-----
From: juniper-nsp-bounces at puck.nether.net [mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of Alex D.
Sent: Saturday, July 09, 2011 10:55 AM
To: Juniper-Nsp
Subject: [j-nsp] External routes in OSPF database

Hello,

we have a MPLS enabled backbone with about 30 routers. IS-IS is used as IGP. All routers have iBGP sessions with our two route-reflectors and get BGP full-feed from them.
Now i try to setup OSPF with area 0.0.0.0 for connecting customers to one of our PE routers (running JUNOS 7.5R2.8). Customer should get only a default route via OSPF.

Now i have the problem that all BGP routes appear as external routes in OSPF database, but only when adjacency to the neighbor router, a Cisco 1841, is up.

Without an adjacency, OSPF database looks like:
   <router># run show ospf database summary
   Area 0.0.0.0:
      2 Router LSAs
   Externals:
      3 Extern LSAs
   Interface ge-0/1/0.22:

When adjacency is up, it looks like:
   <router># run show ospf database summary
   Area 0.0.0.0:
      2 Router LSAs
   Externals:
      14396 Extern LSAs  --> after a while, there appear all BGP routes
   Interface ge-0/1/0.22:

Now my questions:
- Is that the default behaviour of a Juniper router ?
- Why appear all BGP routes in OSPF database as external routes not before adjacency is up ?
- How can i avoid appearence of these routes in OSPF database ?
- How do i achieve that *only* default-route is announced to customer ?


My corresponding OSPF specidic configuration looks as follows:

routing-options {
     static {
         route 0.0.0.0/0 discard;
     }
     router-id <removed>;
}

policy-options {
     policy-statement RM_DEFAULT_ROUTE_TO_OSPF {
         term default-route {
             from {
                 protocol static;
                 route-filter 0.0.0.0/0 exact;
             }
             then accept;
         }
         term explicit-deny {
             then reject;
         }
     }
}

protocols {
     ospf {
         traceoptions {
             file ospf size 500000 files 5;
             flag state;
         }
         export RM_DEFAULT_ROUTE_TO_OSPF;
         area 0.0.0.0 {
             interface ge-0/1/0.22 {
                 authentication {
                     simple-password <removed>;
                 }
             }
             interface all {
                 disable;
             }
         }
     }
}

Thanks in advance for your help...

Regards,
Alex
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