Every time a come across these commands i wonder what is the difference. Now i have looked it up … 🙂
„ip route 0.0.0.0 0.0.0.0 x.x.x.x“ and „ip default-network x.x.x.x“ are the same. They are used when „ip routing“ is enabled. If not use „ip default-gateway x.x.x.x“.
If you add the ip default-network command in EIGRP, you will see the D* in your routing table, as the candidate default. Even if this is not a route to null, it will be used from all routers as it. Seems like a remaining, from the IGRP times, when no summary with 0.0.0.0 0.0.0.0 was possible.
Source:
http://www.cisco.com/en/US/tech/tk365/technologies_q_and_a_item09186a008012d8f7.shtml#qa7
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094374.shtml