severity 432709 normal tags 432709 moreinfo thanks Hi,
On Wed, Jul 11, 2007 at 10:16:48AM -0400, Miguel Martins Feitosa Filho wrote: > > This problem could either be pppoeconf or debian installer related. > [...] > I performed a Debian testing install with net-inst, my internet link is > pppoe. > Debian installer configured pppoe, I assume the installer uses > pppoeconf but that might not be the case. debian-installer doesn't use pppoeconf. If you want report bugs for it, please report against ppp-udeb package. > The system being installed is a small office gateway. > PPPOE came up correctly and was fine during the installation process. > After reboot, internet showed intermittent problems from the other > office computers but not from the gateway itself. The internet worked on > the gateway and not from the other computers in the office. > The problem was intermittent, ping worked, telnet worked, google worked, > other internet sites hanged etc. > This problem was tracked down after a long time to the lack of MTU > setting in my ppp provider file. After running pppoeconf a couple times, > I finally got a configuration that worked for all computers... Your problem is typical when you have a gateway with PPPoE connection and Ethernet LAN. You must clamp the TCP maximum segment size (MSS) at 1452 (or 1412) to avoid too big size for your Ethernet packets. When you use pppoe support in the kernel (like you), pppoeconf add an iptables rule in your /etc/ppp/ip-up.d/0clampmss file. When your use userland pppoe, pppoeconf adjust '-m MSS' option in your dsl-provider file. Then, pppoeconf takes care of this problem in 'LIMITED MSS PROBLEM' step. Please read this step more carefully. > I have only very limited knowledge on ppp and pppoe so the questions > below may seem trivial: > > A) Should pppoeconf set the mtu ? (Mine was commented out). Is there > a situation where pppoe links do not use the MTU when they are > forwarding packets? - See MTU of your ppp* interface with ifconfig command. MTU is often determined via MRU negotiation with your ISP. pppoeconf let ppp do this mechanism and it's OK with a commented value for mtu pppd option by default. - You misundertand what is MTU. See docs on web, for example: http://en.wikipedia.org/wiki/Maximum_transmission_unit MTU is always use by an interface. > B) Do all pppoe links need this limitation ? - MTU of PPPoE can't be higher than 1492 (RFC 1661). See RFC 4638 for discuss about exceptions. > C) How can a novice user be aware of this problem, should pppoeconf > warn him - pppoeconf warns user in 'LIMITED MSS PROBLEM' step. > D) Is their any test that could be done by pppoeconf on the link to > assert the need for this setting and a reasonable value - In 'LIMITED MSS PROBLEM' step, pppoeconf says "If unsure, say yes." and with clamping MSS at 1452 bytes, it will be OK for a very large majority of users. If you have an idea to guess the best settings, send me your patch ;) > E) Is the 1492 limitation correct for all pppoe links? When will it be > higher, when will it be lower? - See above. I think you should read docs about MTU and MSS. I will close this bug except you describe a real problem with pppoeconf. Regards, -- Gregory Colpart <[EMAIL PROTECTED]> GnuPG:1024D/C1027A0E Evolix - Informatique et Logiciels Libres http://www.evolix.fr/ -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
