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

NAME
Net::SMTP::Server::Client - Client session handling 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::Client module implements all the session handling required for a Net::SMTP::Server::Client connection. The above example demonstrates how to use Net::SMTP::Server::Client with Net::SMTP::Server to handle SMTP connections. $client = new Net::SMTP::Server::Client($conn) Net::SMTP::Server::Client accepts one argument that must be a handle to a connection that will be used for communication. Once you have a new client session, simply call: $client->process This processes an SMTP transaction. THIS MAY APPEAR TO HANG -- ESPECIALLY IF THERE IS A LARGE AMOUNT OF DATA BEING SENT. Once this method returns, the server will have processed an entire SMTP transaction, and is ready to continue. Once $client->process returns, various fields have been filled in. Those are: $client->{TO} -- This is an array containing the intended recipients for this message. There may be multiple recipients for any given message. $client->{FROM} -- This is the sender of the given message. $client->{MSG} -- The actual message data. :) 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::Relay perl v5.10.1 1999-12-28 Server::Client(3pm)
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