Messages in this thread |  | | From | Juri Haberland <> | Subject | Re: mtu problem with masquerading+pppoe(adsl) setup | Date | Wed, 3 Oct 2001 15:36:56 +0200 (CEST) |
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In article <200110031300.PAA17063@lambik.cc.kuleuven.ac.be> 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 www.vitrine.be) > > 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
Cheers, Juri
-- Juri Haberland <juri@koschikode.com>
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