The configuration of the default-information originate command in BGP is similar to the configuration of the network (BGP) command. The default-information originate command, however, requires explicit redistribution of the route 0.0.0.0. The network command requires only that the route 0.0.0.0 is present in the Interior Gateway Protocol (IGP) routing table. For this reason, the network command is preferred.
My question is: If the ip default route points to null0, how is it that this command is able to allow pings between bgp routers and F0/0 interface redistributed from OSPF? I thought it was used as a bit bucket to prevent congestion when loops occur? How is it that without this command, I can't ping F0/0 interfaces of BGP routers from the OSPF router? Maybe there is something I've missed about the null0 ip route command?
fredrikjj wrote: » However, you are also injecting a default into BGP with the network command, and that should work since you have the static default to null0. So basically you just have a redundant line of config that you could delete.
fredrikjj wrote: » You shouldn't need a default route in that topology if you advertise the f0/0 networks into BGP and then redistribute these into OSPF on R3. However, looking at the diagram (which is hard, it's kind of small), a potential problem is that when you redistribute BGP into OSPF on R3, the LAN interface of R3 isn't redistributed because it will appear as directly connected in the routing table, not as BGP. Pinging between R3 and R4 will therefore be broken without the default route. If this in fact is the problem you could redistribute connected into OSPF, or just active OSPF on that interface.
OfWolfAndMan wrote: » OK yes I'll take the line of config out as I see what you're saying. My thing was about the default route to null0 though. From R3, I couldn't ping R1's 150.x.x.x LAN unless I added in that default route to null0. Since the null0 route is supposed to be a catch all route, why is it that I can't ping the 150.x.x.x network from R3 without the null0 default route? The network was advertised via OSPF and I redistributed the ospf routes. Maybe I should have specified metric in the redistribution of OSPF into BGP?