Redistributing Default Route

[turbo_engine26]

Hi,

Kindly i need help in clarifying the attached scenario.

As you see, Cairo, Athens and London routers are running RIP. Cairo router is configured for a default route to NYC. I wonder why do i need to redistribute that route to the rest of the RIP neighbors? ... For example, if a packet is received by Cairo from London for a destination behind NYC, Cairo will simply does a route lookup and if no route entry for that packet, it will send the packet to the default route entry then at NYC the destination will be determined. Why London needs a default route too to point to Cairo? ... This scenario is taken from "TCP/IP Routing Vol 1 2nd edition" in chapter 12. The book didn't clarify the reason.

Thx

Regards,

A.M.

[Jon Marshall]

If London did not have a default-route pointing to Cairo then if it received a packet destined for a network at NYC then how would it know where to send the packet ?

Cairo knows to send unknown destinations to NYC but Athens and London don't know that. They need to have a default-route pointing to Cairo as well otherwise they will simply drop the packets and report as unreachable.

Jon

[turbo_engine26]

Haha, you're right. Sorry i was confused about something that made me ask such a question. Because Cairo got a default route, I thought London or Athens would send the packet to Cairo, even if there are no default routes in them. In other words, i thought the default route scenario is special case that makes London forward a packet to Cairo without thinking. Then i realized that the router is just a router that follows the same old mechnaism of forwarding packets.

Thx

Regards,

A.M.