From owner-freebsd-net Wed Aug 26 07:21:14 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id HAA06836 for freebsd-net-outgoing; Wed, 26 Aug 1998 07:21:14 -0700 (PDT) (envelope-from owner-freebsd-net@FreeBSD.ORG) Received: from hcshh.hcs.de (hcshh.hcs.de [194.123.40.1]) by hub.freebsd.org (8.8.8/8.8.8) with SMTP id HAA06826 for ; Wed, 26 Aug 1998 07:21:09 -0700 (PDT) (envelope-from hm@hcs.de) Received: from hcswork.hcs.de([192.76.124.5]) (2262 bytes) by hcshh.hcs.de via sendmail with P:smtp/R:inet_hosts/T:smtp (sender: ) id for ; Wed, 26 Aug 1998 16:20:01 +0200 (METDST) (Smail-3.2.0.101 1997-Dec-17 #2 built 1998-Jun-26) Received: by hcswork.hcs.de (Smail3.1.29.0 #12) id m0zBgT5-0000fAC; Wed, 26 Aug 98 16:22 METDST Message-Id: From: hm@hcs.de (Hellmuth Michaelis) Subject: TCP checksum errors resulting from IP addr change To: freebsd-net@FreeBSD.ORG (FreeBSD Networking) Date: Wed, 26 Aug 1998 16:22:35 +0200 (METDST) Reply-To: hm@hcs.de Organization: HCS Hanseatischer Computerservice GmbH X-Mailer: ELM [version 2.4ME+ PL39 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org I'm trying to debug a strange effect occuring on a sync PPP ISDN interface which is used to connect to a Cisco 1003. To get an address dynamically from the remote side, the local PPP inter- face (on 2.2.5-RELEASE) is set up with: ifconfig isppp0 link1 0.0.0.0 192.76.124.10 netmask 0xffffffff debug Now i telnet to 192.76.124.10 and the link gets established but the telnet session doesn't. I looked at the traces and noticed the very first IP packet going out with source address 0.0.0.0 to the Cisco - i removed that in the driver but still the telnet session is not established. (btw. only the first session is not established, if i terminate the first telnet and restart it on the open link, it works immediately; but i want the first to work ...). I enabled TCP debugging on the Cisco, and for all the packets from this first telnet session it says "TCP checksum error". So i think, IP address 0.0.0.0 is used for checksum calculation of the TCP packets for this forst session, but the "real" IP address of the interface changes to 192.something after the first packet and the TCP checksum is somehow not recalculated causing checksum errors on the remote side. Has anyone a hint or an idea how to solve this ? hellmuth -- Hellmuth Michaelis Tel +49 40 559747-70 HCS Hanseatischer Computerservice GmbH Fax +49 40 559747-77 Oldesloer Strasse 97-99 Mail hm [at] hcs.de 22457 Hamburg WWW http://www.hcs.de To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message