A co-worker of mine insists that a router, by default, will not forward traffic that is destined for a private IP address unless that private IP is specifically configured, either via a routing protocol or static routing. He thinks that if you only have a default route configured and try to send to a private IP address, the router will drop it, because it's considered "non-routeable".
For example, say you had no static routes and no routing protocol configured, only a static default route (0.0.0.0) and a single path out, and then tried to send a packet to 192.168.0.1. My co-worker thinks that the router would drop this packet.
I think that the router doesn't enforce those rules, at least not by default. The router doesn't know whether it's on a private LAN or if it's an edge router on the Internet. I think those "non-routeable" rules have to be configured, otherwise the router will attempt to match the packet against it's routing/forwarding table, and if it doesn't find a match, will just forward it out according to its default route.
So who's right - me or my co-worker? Please say me...ha ha.
