ICMP is used to determine maximim packet size. If you or the other end are blocking all ICMP then MTU Path Discovery will not work. It's a classic newbie network admin mistake. Symptoms of this problem would be exactly like you describe.
Typically I see this on PPPoE connections. More info: http://www.znep.com/~marcs/mtu/ Roger Schreiter wrote: > Hi, > > I'm using app_pppd with a Digium-PRI-card for PPP connections. > I had some strange problems with some IP packets passing > and some not, e.g. ftp login went well, but as soon as > I tried to up- or download a file, noting was transferred. > > I finally guessed, it must have to do something with the packet > size. Then I started pppd with the parameters mtu 296 and mru 296 > as in further times with the analogue modems. > > Then, everything went fine (for a while). > > > Unfortunately, PPP via ISDN is typically using a MTU and a MRU > of 1500, and I found, that some commercial ISDN routers do not > allow negotiating MTU and MRU. They insist to use a size of 1500. > > > Since, using CAPI or ISDN4Linux (not via asterisk), pppd is working > well with the MTU/MRU value of 1500, I assume, there is some packet > size limitation in the asterisk part (including app_pppd). > > I tried to find any too small buffer or similar, but successless. > > > May I ask you, where do you think, the limitation does come from: > - from app_pppd (I don't think so) > - from libpri > - from chan_dahdi > - from the dahdi kernel modules > - from the asterisk kernel > > > Any hint is welcome! > > Regards, > Roger. > > > _______________________________________________ > -- Bandwidth and Colocation Provided by http://www.api-digital.com -- > > asterisk-users mailing list > To UNSUBSCRIBE or update options visit: > http://lists.digium.com/mailman/listinfo/asterisk-users > > -- Consulting and design services for LAN, WAN, voice and data. Based near Birmingham, AL. Now accepting clients worldwide. Contact me for Tellabs echo canceling systems. Also see http://www.fnords.org/skillslist.html _______________________________________________ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- asterisk-users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
