From owner-freebsd-net Wed Aug 8 13:38:28 2001 Delivered-To: freebsd-net@freebsd.org Received: from smtp1.sentex.ca (smtp1.sentex.ca [199.212.134.4]) by hub.freebsd.org (Postfix) with ESMTP id 7F75E37B401 for ; Wed, 8 Aug 2001 13:38:18 -0700 (PDT) (envelope-from mike@sentex.net) Received: from simoeon.sentex.net (pyroxene.sentex.ca [199.212.134.18]) by smtp1.sentex.ca (8.11.2/8.11.1) with ESMTP id f78KcG694670; Wed, 8 Aug 2001 16:38:16 -0400 (EDT) (envelope-from mike@sentex.net) Message-Id: <5.1.0.14.0.20010808162550.0433abb0@marble.sentex.ca> X-Sender: mdtpop@marble.sentex.ca X-Mailer: QUALCOMM Windows Eudora Version 5.1 Date: Wed, 08 Aug 2001 16:32:01 -0400 To: Jun-ichiro itojun Hagino From: Mike Tancsa Subject: Re: gif MTU of 1280 ? Cc: freebsd-net@freebsd.org In-Reply-To: <20010808202655.893BF7BC@starfruit.itojun.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org At 05:26 AM 8/9/01 +0900, Jun-ichiro itojun Hagino wrote: > >But where would the PMTU source address come from ? If someone is rejecting > >all RFC 1918 space at their border, if a ICMP message originates with such > >source address, would this not be problematic ? > > I don't understand what you are trying to discuss. diagram please. > >itojun 172.16.1.1/24 <--> 10.0.0.1/30 - - - 10.0.0.2/30<--->192.168.1.1 With 192.168.1.1 and 172.16.1.1 being non RFC 1918 addresses in this example and the 10.0.0.1 IPs being the internal addresses. Lets say a machine (216.136.204.21 wants to get to 192.168.1.1, and it comes in via the public gateway 172.16.1.1. To get to 192.168.1.1, it must be fragmented. The question is, when the ICMP message is sent out, with what source address does the packet leave ? e.g. if 216.136.204.21 is configured to ignore all traffic from the RFC 1918 space, and the ICMP message goes out with a source address of 10.0.0.1 or 10.0.0.2, then 216.136.204.21 will never hear it. ---Mike To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message