From owner-freebsd-hackers Thu Mar 25 10:36:22 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from orbit.flnet.com (orbit.flnet.com [205.240.232.32]) by hub.freebsd.org (Postfix) with ESMTP id ADC7A14DDB for ; Thu, 25 Mar 1999 10:36:20 -0800 (PST) (envelope-from henrich@orbit.flnet.com) Received: (from henrich@localhost) by orbit.flnet.com (8.8.5/8.8.4) id NAA11209 for freebsd-hackers@freebsd.org; Thu, 25 Mar 1999 13:36:01 -0500 (EST) Date: Thu, 25 Mar 1999 10:36:01 -0800 From: Charles Henrich To: freebsd-hackers@freebsd.org Subject: A Question about MTU and ICMP Need to Frag Message-ID: <19990325103601.C11010@orbit.flnet.com> Mail-Followup-To: freebsd-hackers@freebsd.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.95.4i X-Operating-System: FreeBSD 2.2-BETA_A X-PGP-Fingerprint: 1024/F7 FD C7 3A F5 6A 23 BF 76 C4 B8 C9 6E 41 A4 4F Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG I have a question.. I have a system with two interfaces fxp0 and fxp1, fxp1 is the external interface (to the world) fxp0 is the internal interface (net 10). If I alter the mtu on the external interface to something rediculous like 128 bytes, then connect to sites around the net, as far as I can tell, no ICMP need to frag packets are being generated (watching with tcpdump), but everything is working peachy keen. However, if I alter the mtu on the internal interface.. Connections out to the internet cause ICMP need to frag packets to be generated. The question I have is, shouldnt an ICMP need to frag packet be generated in all cases? If not, what magic is going on to get the outside world to talk in the smaller packet size? Thanks! -Crh Charles Henrich Manex Visual Effects henrich@flnet.com http://orbit.flnet.com/~henrich To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message