Default Gateways, Default Routes, and Route(s) of Last Resort

The UNIX routing table is intimately connected to the Address Resolution Protocol (ARP) cache for next-hop Layer 2 address resolution. This becomes obvious when looking at the timer (expire) column of BSD routing table output. In contrast to Cisco IOS Software, UNIX does not employ the concept of a default network. There is no notable difference between the terms default route and route of last resort. The naming difference has historical reasons. The Cisco IOS ip default-gateway command is used when IP routing is disabled and should not be confused with ip route default, which actually adds an explicit default routing entry.