From: Luigi Corsello <mlreader@lucomp.net>
To: netfilter@lists.netfilter.org
Subject: Re: broken SNAT with fixed external MTU
Date: Thu, 14 Oct 2004 21:52:05 +0200 [thread overview]
Message-ID: <416ED8E5.7000501@lucomp.net> (raw)
In-Reply-To: <20041014181747.GA3929@bender.817west.com>
Jason Opperisano wrote:
> On Thu, Oct 14, 2004 at 06:15:22PM +0200, Luigi Corsello wrote:
>
>>Hello everybody,
>>
>>My DSL router (very bad firmwares) wants me to force the MTU
>>(buggy MTU auto-setting). The firewall has a public IP and mtu 1500:
>>
>>---snip
>>#route to the router net
>>ip route add 192.168.1.0/24 dev eth1 mtu 1440
>># default to the router (mtu not needed here)
>>ip route add default via 192.168.1.1 mtu 1440
>>--snip
>>
>>the firewall itself NATs one client back-to-back connected
>>
>>---snip
>>#mss clamping 1)
>>iptables -A FORWARD -d $net1 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS
>>--set-mss 1440
>>iptables -A FORWARD -s $net1 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS
>>--set-mss 1440
>
>
> try not to confuse MTU with MSS, as they are not the same. if you're
> going for an MTU of 1440--you should be setting MSS to 1400 (MSS = MTU -
> 40).
Ykes! that was it. Too many sleepless nights flashing crappy firmwares.
Thanks a lot!
/lc
>
> -j
>
prev parent reply other threads:[~2004-10-14 19:52 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-14 16:15 broken SNAT with fixed external MTU Mailing List Reader
2004-10-14 18:17 ` Jason Opperisano
2004-10-14 19:52 ` Luigi Corsello [this message]
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