Well, putting this iptables rule at the head of my FORWARD chain solves the problem: iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
I still have absolutely no idea why this worked fine on one router, and fails on another though! On 26 September 2013 10:48, Toby Corkindale <[email protected]> wrote: > Hi, > This is perhaps more of a networking question than Linux, but all the > devices involved are running Linux.. > > I have what is probably a common home setup -- an ADSL modem operating > in "pure bridge" mode, connected by ethernet to a Linux server running > pppd with the PPPoE plugin. Same linux server is providing DNS, DHCP > and NAT for other clients connected via wireless and ethernet. > > This setup was running fine for many years with a Billion 7300RA ADSL > modem. I just switched it over to a newer Billion 7800NL modem in the > hope it'd provide better sync speeds on my hopeless phone line. (It > does, with some SNR tweaking) > > However for some reason path MTU discovery has completely broken when > using the newer modem. > The primary Linux box is fine, but all clients (whether wired, > wireless *or even virtual*) fail to work unless I manually set their > interfaces to an mtu of 1492. > > I'm pretty confused by this -- pppd was setting itself up with a 1492 > mtu even on the old modem, and that managed to propagate out just > fine. The only thing that changed was the modem, but that shouldn't > affect this issue. > > I'm bamboozled. Could anyone advise me on what could possibly be done > to figure out what has happened? > Or better, a way to fix it? > > Investigative notes: > 1) New router was switched back to standalone mode (where it does > pppoe, dhcp, nat etc) and in this mode, all clients worked fine. So > the ADSL link and ethernet ports seem OK. > 2) Old router was booted up to verify settings and that stuff works OK > with it. Settings for ADSL line were similar, and stuff does work with > it. (I say settings were "similar" because the two modems have > different interfaces, and the 7800NL has some extra options not > present on the 7300RA, but I don't think they're relevant to this > issue) > > Thanks in advance, > Toby > > -- > Turning and turning in the widening gyre > The falcon cannot hear the falconer > Things fall apart; the center cannot hold > Mere anarchy is loosed upon the world -- Turning and turning in the widening gyre The falcon cannot hear the falconer Things fall apart; the center cannot hold Mere anarchy is loosed upon the world _______________________________________________ luv-main mailing list [email protected] http://lists.luv.asn.au/listinfo/luv-main
