Date: Mon, 17 Aug 1998 20:18:14 -0400 (EDT) From: Jeff Aitken <jaitken@dimension.net> To: sthaug@nethelp.no Cc: girgen@partitur.se, freebsd-security@FreeBSD.ORG Subject: Re: private network on router's external NIC? Message-ID: <199808180018.UAA14592@gizmo.dimension.net> In-Reply-To: <6847.903394909@verdi.nethelp.no> from "sthaug@nethelp.no" at "Aug 18, 98 01:01:49 am"
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sthaug@nethelp.no writes: > > Makes sense to me. So, how do these ip numbers get out on the Internet? > > How do they get routed anywhere; they're supposed to be private? Those addresses are only private because we all consider them to be. There's nothing stopping an ISP from telling the world "The 10.0.0.0/8 network is reachable via ME!". Hell, there have been people who have announced "Hey, the ENTIRE INTERNET is reachable through ME!". ;-) What's stopping them is the fact that *most* people won't route to private network addresses. > Routing is normally done on *destination* address, so a *source* address > within the RFC 1918 address ranges is irrelevant to routing. > > There are several reasons why such packets show up, e.g.: > > - ISPs with the (bad) idea that they can use RFC 1918 for their internal > network links, because (supposedly) the addresses won't get out. Guess > what happens when you do a traceroute along one of these paths? Not to get off topic, but using private addresses for internal network links doesn't necessarily cause them to be advertised. If this guy is seeing attempted connections to WWW servers, they're not the result of someone running a traceroute. Only improperly configured routers (and less-than-clueful upstream providers) cause these networks to be advertised. I'm not defending the improper use of private network numbers, but it takes more than that to account for the observed behavior. --Jeff To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe security" in the body of the message
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