Propagating 0.0.0.0 routes from EIGRP into IGRP

Did you try the "ip default-network" command ?

Yes, we tried to use ip default-network but that didn't work. We still were unable to propagate a Gateway of Last resort into the IGRP network.

Actually to get the desired result, you will need to redistribute default into EIGRP first.

ip route 0.0.0.0 0.0.0.0

router eigrp 1 redistribute static exit

We have the "redistribute static" in our eigrp config. Other routers in the eigrp AS have the default route, we just can't get it to propagate the default route into IGRP.

Some router in that network must be running both EIGRP and IGRP. On that router, you will need to redistribute the OSPF routers into IGRP routes.

router igrp 100 network w.y.y.z redistribute ospf 100

EIGRP has a better admin distance than IGRP, so you might want to take the extra step of either adding in a distribute-list so only the default route is sent via igrp, or tune the distances with the distance command.

We do have a router that is running both EIGRP and IGRP and they are in the same AS. The normal routes are seen across the network, only the default route is not distributed to the IGRP network. All interfaces in the EIGRP network can be pinged from the IGRP network, except for the default routes destination. Yet, the EIGRP network can ping the default route destination. FYI, the destination is pointing to a simulated ISP, thus it doesn't have a routing protocol.

We figured out what the problem was. We were using "ip default-network" incorrectly, we had the wrong network plugged in. Also our static route that was allowing the "ISP" to reply was not set to include the networks that we were testing from. Thankyou everyone for all of your help.

Is the router where the ip default-network command different from the router where you are running both the EIGRP and IGRP routing process ?