Date: Tue, 30 Jun 1998 15:53:27 +0400 From: "Oleg Semyonov" <os@ktpk.dp.ua> To: "Eivind Eklund" <eivind@yes.no>, <freebsd-questions@FreeBSD.ORG> Subject: MTU? (Re: FreeBSD+natd = tcp connection problems) Message-ID: <01bda41d$b15fe2e0$0400a8c0@admin.dnepr.com>
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Eivind, you wrote: >On Wed, Jun 24, 1998 at 03:59:17PM +0400, Oleg Semyonov wrote: >> Hi all! >> >> I have some problems with tcp connections to some servers >> (ftp, irc and some others). My network configuration is quite >> simple: FreeBSD box is connected via slip (sl0) to IP provider >> (BSDI 2.1) and via NIC (de0) - to LAN (Win95/NT workstations). >> I have one real IP for FreeBSD box and private network >> 192.168.0.* for LAN. Natd is used for NAT, and all was ok, but... >> >> PROBLEM DESCRIPTION: >> >> When I trying to ftp to some servers from FreeBSD, in some >> cases I can enter login/password, and then see only first >> 230- >> line, and connection hangs. When using password in form of >> -user@ (disable that 230- messages) - all ok. For example, >> connect to ftp.kiae.su and ftp.hp.com was failed, connect >> to ftp.microsoft.com - ok. >> Then I found that we are using different MTU values on >> both sides of slip link (308 by defaul on BSDI, 507 by default >> on FreeBSD). I'm setting my side to 308. All ok, ftp with no >> problems. But only from FreeBSD box. Workstations from LAN via >> natd cannot ftp with same problem: 230- and stop. Workstations >> on LAN and de0 interface on FreeBSD are using MTU=1500. >> Next stage was to replace slip by ppp with mtu=1500. Effect >> was same: dropped connections from FreeBSD (and LAN too). Changing >> ppp0 MTU to 296-308 solves problem, but for FreeBSD box only. >> LAN cannot ftp to such servers. Irc connections from LAN hangs >> in same manner. >> >> What is the reason and what can I do? Does anybody help me? > >This belongs in FreeBSD-questions - I've moved it there. > >I also believe the problem is probably your FTP clients rather than >the NATD code, but I can't guarantee this. natd is somewhat dependent >on how that packets are constructed, but this shouldn't matter at >_that_ stage - only when you do an LS or GET. > >Eivind. Nope! Sure. Is original FreeBSD's ftp client bad or non-tested? But it don't work too with 1500 mtu in my case. And without natd and ipfw in single client mode (single IP address) I have troubles with relatively large MTU size (>308). Seems it is not a natd-related problem, but some packet assembly/disassembly effects with my OS pair: FreeBSD + BSDI 2.1. Maybe it is a problem of remote side? But how can I check and fix it? OS To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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