Hi,
I connect through a Cable modem to a pptp server, have a pptp-command tunnel active and configured routing table.
The thing is, I can ping my pptp sever IP and can see that tcpdump is logging network activity, but when trying any other site, no names would resolve into IP's. i.e: www.slackware.com, or any other name (assuming it could be behind a firewall). I get an "unkown host" message.
'ifconfig' shows that ppp0 has large amounts (not huge, I checked for loop possible problem) of transmit data but only some 4 packets appear in Rx.

I opened Mozzila browser and configured proxies, but it is as if the browser can't reach the server and won't recognize the proxy address.

These two lines appear in var/log/messages when the tunnel starts:

May 2 09:19:49 liron pptp[1275]: anon log[mainptp.c:237]: The synchronous pptp option is NOT activated
May 2 09:19:49 liron pptp[1287]: anon log[pptp_make_packetptp_ctrl.c:550]: reserved0 field is not zero! (0x8d16) Cisco feature?

Do you know how do I activate sync in pptp/pppd?
Where can I find the iptables file, maybe it is a firewall problem?
I read RFC1326, and it states that "the Reserved0 field in the header MUST be 0." but I have no idea what could be the prob. here as I have the altest packages from pptpclient.

Can you please help??

I have similar setup with your. Actually I do PPTP over wifi. The problem is when you login, you probably have an error message say, /etc/resolv.conf doesn't match(from previous nic card, probably have to do with dhcp setting). the workaround is to copy the /etc/resolv.conf.pptp to /etc/resolv.conf manually. and that sould work.

I use pptp-command. It allows you to configure resolve.conf then once you run the tunnel, it will copy it automatically to the real used one.
I wonder if it's a routing problem or has something to do with activation of the sync option...or the Reserved0 field.

Still wating for ppp mail list answers, maybe James Cameron himself will help :-)

I know, I use pptp-command too, but at the end of the pptp-command, if it complain about the resolv doesn't match, it will not copy the new one over.
in the mean time, the workaround is to copy it manually.
do a "cat etc/resolv.con" and see what you get.

Everything works now...that's cool. It was a routing problem, so once I changed the default gw to be the local IP assigned by pptp server, tcpdump here started dancing and throwing gre packets all over the place. It is a true feeling of elation. :-)