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connection to vpn Server (pptp) behind iptables FW

DISCUSSION [email protected] 2 participants 2 messages Mar 12, 2004

lore
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lore

[email protected]

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#0 lore raw

Hi,

since two weeks i try to create rules for my iptables fw who
let pass an vpn tunnel to my internel ms vpn server (pptp).
i have installed the kernel 2.4.25 and patched it with patch-o-matic (only the pptp/gre patch aplied).

i load the ip_conntrack_pptp, ip_conntrack_proto_gre, ip_nat_pptp and ip_nat_proto_gre modules, and my script looks so:
iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 1723 -j DNAT --to-destination 192.168.1.2 iptables -A FORWARD -i eth0 -m state --state NEW -p tcp -d 192.168.1.2 --dport 1723 -j ACCEPT iptables -A FORWARD -i eth0 -m state --state NEW -p GRE -d 192.168.1.2 -j ACCEPT iptables -t nat -A PREROUTING -i eth0 -p GRE -j DNAT --to-destination 192.168.1.2 iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -I FORWARD 1 -m state --state ESTABLISHED,RELATED -j ACCEPT

So whats wrong, becaus i can connect to the vpn server behind the firewall, but the connection hangs at the authentification. after some minutes i receive an message that the server does not respond.

netstat say this:
netstat-nat -d 192.168.1.2
Proto NATed Address Foreign Address State
tcp p42821a5e.dip.t-dialin.ne:4394 192.168.1.2:1723 ESTABLISHED tcp p42821a5e.dip.t-dialin.ne:4392 192.168.1.2:1723 TIME_WAIT

Scheme of my network:
vpn-client -> hw-router -> internet -> hw-router -> firewall -> vpn-server

so whats going wrong?

Thanx Peter

#1 lore raw
Quoted 16 lines · On Fri, 2004-03-12 at 11:40, [email protected] wrote:

Hi,

since two weeks i try to create rules for my iptables fw who
let pass an vpn tunnel to my internel ms vpn server (pptp).
i have installed the kernel 2.4.25 and patched it with patch-o-matic (only the pptp/gre patch aplied).

i load the ip_conntrack_pptp, ip_conntrack_proto_gre, ip_nat_pptp and ip_nat_proto_gre modules, and my script looks so:
iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 1723 -j DNAT --to-destination 192.168.1.2 iptables -A FORWARD -i eth0 -m state --state NEW -p tcp -d 192.168.1.2 --dport 1723 -j ACCEPT iptables -A FORWARD -i eth0 -m state --state NEW -p GRE -d 192.168.1.2 -j ACCEPT iptables -t nat -A PREROUTING -i eth0 -p GRE -j DNAT --to-destination 192.168.1.2 iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -I FORWARD 1 -m state --state ESTABLISHED,RELATED -j ACCEPT

Quoted 4 lines

So whats wrong, becaus i can connect to the vpn server behind the firewall, but the connection hangs at the authentification. after some minutes i receive an message that the server does not respond.

Micro$oft has a 'technote' on this in their technet section on the website. AFAIR you need to allow protocol 37 to be forwarded between the two.

Quoted 12 lines

netstat say this:
netstat-nat -d 192.168.1.2
Proto NATed Address Foreign Address State
tcp p42821a5e.dip.t-dialin.ne:4394 192.168.1.2:1723 ESTABLISHED tcp p42821a5e.dip.t-dialin.ne:4392 192.168.1.2:1723 TIME_WAIT

Scheme of my network:
vpn-client -> hw-router -> internet -> hw-router -> firewall -> vpn-server

so whats going wrong?

Thanx Peter

Signature · 7 lines
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Raymond Leach <[email protected]>
Network Support Specialist
http://www.knowledgefactory.co.za
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