[lkml]   [2001]   [Oct]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: mtu problem with masquerading+pppoe(adsl) setup
In article <> you wrote:
> Hello, (i am sorry if this is the wrong place to ask)
> despite the frequent discussions concerning this topic on usenet, i failed
> to solve my problem:
> - i have a debian potatoe box that acts as a masquerading server for a
> heterogenous win2k/winnt/mac LAN. pppoe works fine, and so does
> masquerading ... almost
> - the kernel i installed is the latest 2.2 kernel (2.2.19)
> the problem:
> i can't access some sites from the masq clients, while i can access them
> from the masq server. (like
> The problem seems to be widely known, and seems to be an MTU+no-fragment
> packets issue. and indeed:
> - the MTU on my LAN is 1500 bytes
> - the MTU on my ppp connection is 1492 bytes.
> on the archives, i found the following solutions:
> - raising the ppp MTU to 1500 bytes. it won't work. even if i specify 1500,
> the mtu is still 1492.
> - lowering the mtu of the LAN to 1492 bytes. thats not an option according
> to my boss.
> - upgrade to something newer than 2.2.14. i run 2.2.19 and i still have the
> problem.
> So my questions are:
> - are there other options ? i read some vague german things about msschamp
> or something like that, but i don't know if they are even related.
> - will an upgrade to linux 2.4 or the kernelspace pppoe driver fix my
> problem ? (i would like to keep my current setup, i don't know how
> difficult it is to upgrade a potatoe box to such a recent version ..)

Well, upgrading to a recent 2.4 kernel gives you the possebility to use
the TCPMSS target in iptables which resolves your problems.

I'm also running a Linux masquerading box on a ADSL (T-DSL) line and I have
no problems at all (I can access the site you mentioned fine) with
the following line in iptables:

$IPTABLES -I FORWARD -j TCPMSS -o $FW_WORLD_DEV --clamp-mss-to-pmtu -p tcp --tcp-flags SYN,RST SYN


Juri Haberland <>

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:03    [W:0.020 / U:5.752 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site