Re: Please help: ptp links addresses From owner-lir-wg@localhost Thu Jul 11 23:01:33 1996

Daniel,

>   Also note that even for private address space traceroute will return the
>   address correctly, so the diagnostics are useful.  There just are no
>   names. If the border gateways with publicly adressed interfaces has a
>   reasonable name such as 'bordergw-xxx.clever.net' 'clever-gw.customer.nl'
>   it is quite clear "where you are" in between.

Although I agree in general with your statement above, I think the details are
not necessarily true. According to RFC 1918:

   Because private addresses have no global meaning, routing information
   about private networks shall not be propagated on inter-enterprise
   links, and packets with private source or destination addresses
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^
   should not be forwarded across such links. Routers in networks not
   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   using private address space, especially those of Internet service
   providers, are expected to be configured to reject (filter out)
   routing information about private networks. If such a router receives
   such information the rejection shall not be treated as a routing
   protocol error.

If an ISP is taking this recommendation by the letter, then they install
a filter on the border routers to filter out these packets (as we do ourselves).
In this case though, a traceroute from outside will not receive any packets
from the interfaces that have a IP address from the private addresse space.

I agree however that the answers from the other routers will give you in most
of the cases enough information to figure out what route the packets take.

Regards,
Janos