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I have many pptp vpn tunnels or servers to connect to and linux would assign ppp0 for the 1st connection, ppp1 for 2nd connection and so on. I need the interfaces to be fixed so i can forward the connection properly via iptables. Is there a way to fix the interface name to each tunnel?

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That's not the way this is done. The way to do it is specified in the ever-helpful Arch Linux wiki, under the heading Split Tunneling based on port by /etc/ppp/ip-up.d.

Let me explain. All files in /etc/ppp/ip-up.d are executed every time a pptp connection is established, and the file 01-routebyport.sh is passed the following arguments,as per the Web page above:

  # This script is called with the following arguments:
  # Arg Name
  # $1 Interface name
  # $2 The tty
  # $3 The link speed
  # $4 Local IP number
  # $5 Peer IP number
  # $6 Optional ``ipparam'' value foo

Thus, since you are passed the peer IP number and the interface name, you can build your iptables rules by means of case: 

  case $5 in:
        1.1.1.1) 
                   iptables -i $1 -j DROP
        8.8.8.8) 
                      iptables -i$1-j ACCEPT

and so on.

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  • So i guess it's not possible to use a custom interface name? Thanks for the url & script. I am a little familiar with shell scripting, i shall see what i can do.
    – 13th Matrix
    Sep 15, 2015 at 10:55
  • @13thMatrix It is better than it's not possible to use a custom interface name: you do not have to know what each interface is called, you can let your own pc do that for you, an still make it work. Less work for you.
    – MariusMatutiae
    Sep 15, 2015 at 11:05
  • I finally manage to script up everything. It's a little more complicated as thought because i have numerous VPN connections which need many iptables rules for forwarding. Thanks.
    – 13th Matrix
    Nov 6, 2015 at 5:39

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