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Special Forums IP Networking 3 public servers: middle machine for traffic forwarding Post 303008256 by pedroz on Wednesday 29th of November 2017 10:36:31 AM
Old 11-29-2017
3 public servers: middle machine for traffic forwarding

With the following machines...
Server 1: PPTP client windows; Public IP: 1.1.1.1
Server 3: PPTP server centos6; Public IP: 3.3.3.3
Connecting VPN server3 from server1 works correctly!

Goal is to have a middle server forwarding traffic in both ways
Server 1: PPTP client windows; Public IP: 1.1.1.1
Server 2: Traffic forwarding centos6; Public IP: 2.2.2.2
Server 3: PPTP server centos6; Public IP: 3.3.3.3

Server1 connects with PPTP client to 2.2.2.2 and this server2 redirects to 3.3.3.3 (server3)
Is it possible to have that scenario?


Tried the following setup in Server2
1. Routing enabled
Code:
# echo "1" > /proc/sys/net/ipv4/ip_forward
# nano /etc/sysctl.conf
net.ipv4.ip_forward = 1
# sysctl -p

2. Iptables forward
Code:
# iptables -F -t nat
# iptables -F
# iptables -A FORWARD -d 3.3.3.3 -i eth0 -j ACCEPT
# iptables -t nat -A PREROUTING -i eth0 -d 2.2.2.2 -j DNAT --to-destination 3.3.3.3
# iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
# iptables save
# iptables reload

When trying to connect with Server1 VPN PPTP client to 2.2.2.2, it redirects correctly to 3.3.3.3.
However, in server3 (3.3.3.3) it does not assign a PPTP client to 2.2.2.2.
Here is the connection log at server3

Code:
# tail -f /var/log/messages
Nov 29 09:53:39 office pptpd[2121]: CTRL: Client 2.2.2.2 control connection started
Nov 29 09:53:39 office pptpd[2121]: CTRL: Starting call (launching pppd, opening GRE)
Nov 29 09:53:39 office pppd[2122]: Plugin /usr/lib64/pptpd/pptpd-logwtmp.so loaded.
Nov 29 09:53:39 office pppd[2122]: pppd 2.4.5 started by root, uid 0
Nov 29 09:53:39 office pppd[2122]: Using interface ppp2
Nov 29 09:53:39 office pppd[2122]: Connect: ppp2 <--> /dev/pts/3
Nov 29 09:54:09 office pppd[2122]: LCP: timeout sending Config-Requests
Nov 29 09:54:09 office pppd[2122]: Connection terminated.
Nov 29 09:54:09 office pppd[2122]: Modem hangup
Nov 29 09:54:09 office pppd[2122]: Exit.
Nov 29 09:54:09 office pptpd[2121]: GRE:  read(fd=6,buffer=6124a0,len=8196) from PTY failed: status = -1 error =  Input/output error, usually caused by unexpected termination of pppd,  check option syntax and pppd logs
Nov 29 09:54:09 office pptpd[2121]: CTRL: PTY read or GRE write failed (pty,gre)=(6,7)
Nov 29 09:54:09 office pptpd[2121]: CTRL: Client 2.2.2.2 control connection finished

Any ideas to setup the server2 working as middle traffic forwarder?
 

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Server::Relay(3pm)					User Contributed Perl Documentation					Server::Relay(3pm)

NAME
Net::SMTP::Server::Relay - A simple relay module for Net::SMTP::Server. SYNOPSIS
use Carp; use Net::SMTP::Server; use Net::SMTP::Server::Client; use Net::SMTP::Server::Relay; $server = new Net::SMTP::Server('localhost', 25) || croak("Unable to handle client connection: $! "); while($conn = $server->accept()) { # We can perform all sorts of checks here for spammers, ACLs, # and other useful stuff to check on a connection. # Handle the client's connection and spawn off a new parser. # This can/should be a fork() or a new thread, # but for simplicity... my $client = new Net::SMTP::Server::Client($conn) || croak("Unable to handle client connection: $! "); # Process the client. This command will block until # the connecting client completes the SMTP transaction. $client->process || next; # In this simple server, we're just relaying everything # to a server. If a real server were implemented, you # could save email to a file, or perform various other # actions on it here. my $relay = new Net::SMTP::Server::Relay($client->{FROM}, $client->{TO}, $client->{MSG}); } DESCRIPTION
The Net::SMTP::Server::Relay module implements simple SMTP relaying for use with the Net::SMTP::Server module. All this module does is to take a given message and iterate through the list of recipients, doing DNS lookups for the associated MX record and delivering the messages. This module makes extensive use of the plethora of other modules already implemented for Perl (specifically the DNS and Net::SMTP modules in this case), and should give but a glimpse of the potential for extending the Net::SMTP::Server's functionality to provide a full-featured SMTP server, native to Perl. The above example illustrates the use of the Net::SMTP::Server::Relay modules -- you simply have to instantiate the module, passing along the sender, recipients, and message. More formally: $relay = new Net::SMTP::Server::Relay($from, @to, $msg); Where $from is the sender, @to is an array containing the list of recipients, and $msg is the message to relay. AUTHOR AND COPYRIGHT Net::SMTP::Server / SMTP::Server is Copyright(C) 1999, MacGyver (aka Habeeb J. Dihu) <macgyver@tos.net>. ALL RIGHTS RESERVED. You may distribute this package under the terms of either the GNU General Public License or the Artistic License, as specified in the Perl README file. SEE ALSO
Net::SMTP::Server::Server, Net::SMTP::Server::Client perl v5.10.1 1999-12-28 Server::Relay(3pm)
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