Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Forwarding of traffic with private IP destination addresses

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.

1 REPLY
Hall of Fame Super Gold

Re: Forwarding of traffic with private IP destination addresses

You are right.

Router doesn't enforce anything and unless destination address is all 0s or multicast, will forward it with a default route.

127
Views
0
Helpful
1
Replies