Private IPs

[droby10]

a default routing setup will route regardless of network and host address; the rfc indicates that the reserved blocks _should_ not be routed in public networks; and are in most cases implemented as such on the public routers on the Internet.

the traceroute output in the original post indicates that the 10 dot network host is within a local context to the two adjacent hosts listed.

aside from that, in this example we are not routing _to_ the 10.x.x.x network - we are routing through the 10.x.x.x network as a private infrastructure; because this host/network is local (physical) on both ends to public address space, the IP is irrelevant other than being associated with a mac address in the arp tables of the two adjacent hosts listed.

[bighabu]

The addresse used in the private range can be routed on an internal private network. Where I work we use 10.x.x.x for all of our sites. We have 42 remote sites connected to us on a private WAN. All sites use a different subnet of addresses and our main router routes traffic between all sites. When someone accesses the internet then our firewall NAT's it to a routable Internet address assigned to us by our ISP. I can ping any machine at any facility and I remotely connect to their servers all the time.

The reason that the traceroute shows a non routable address is probably because the router is not routing properly or it is misconfigred. The router is just sending back the ICMP packets that it is programmed to send. Also the router may not have a route back to the sender on the interface that it received the packets from. So the router will report back the interface that does have a route back to the sender which in this case it looks like an internal interface on a privately addressed network. Remember that TCP/IP was not designed to use traceroute, it is a hack that was designed to help with network troubleshooting. It is not accurate and you can get back bad information.