[nsp] 192.168.x.y from upstream

Gert Doering gert at greenie.muc.de
Mon Mar 10 13:56:09 EST 2003


On Mon, Mar 10, 2003 at 02:42:01PM +0300, Rivo Tahina RAZAFINDRATSIFA wrote:
> Why do I receive something from private IP address such as 192.168. from my
> upstream?

Because many ISPs are lazy and do not properly filter packets before
the packets leave their networks.

Proper network management consist of (relating to RFC1918 only):

 - don't use RFC 1918 addresses for the ISP backbone networks
   (because traceroute and other ICMP responses might end up being
   sent with those addresses, which violates RFC 1918)

 - filter your customer access lines so that customers can only generate
   packets with source IPs that belong to them ("anti-spoofing"), see
   also RFC 2827 "Network Ingress Filtering".

USENET is *not* the non-clickable part of WWW!
Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert.doering at physik.tu-muenchen.de

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