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I have VPN server on Debian stable. People in LAN (gray network) use this server for access to internet (WAN). But I also want to use this VPN server as something like "proxy" (connect from internet, and browse the web). I can connect to server from internet, but internet not work: client get IP from server, also can ping other clients, but can't ping default gateway (which is server's IP address inside GRE tun). Adding default route to gateway doesn't help.

My PPTPD configuration:

─➤  grep -v '^$\|^\s*\#' /etc/pptpd.conf 
option /etc/ppp/pptpd-options

─➤  grep -v '^$\|^\s*\#' pptpd-options                                                             
name pptpd

─➤  sysctl -a | grep ip_forward
net.ipv4.ip_forward = 1

Iptables rules:

iptables -t nat -I POSTROUTING -s -j MASQUERADE                              
iptables -I FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu

In logs everything just fine: client connects, getting IP. Server also connecting to internet via ISP VPN servers.

share|improve this question
Can you see the traffic being denied in iptables? – NickW Oct 30 '13 at 13:24
up vote 0 down vote accepted

Reading your story my guess is you should explicitly allow ppp interfaces:

-A INPUT   -i ppp+ -j ACCEPT
-A OUTPUT  -o ppp+ -j ACCEPT
-A FORWARD -i ppp+ -j ACCEPT
-A FORWARD -o ppp+ -j ACCEPT
share|improve this answer
That was so simple. Thank you! :) – bosha Oct 31 '13 at 17:46

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