How to configure traffic routing from webproxy to a specific pptp interface, depending on the port?

Question

Mikrotik

scheme
(eth1)192.168.1.2:1001<->pptp1
(eth1)192.168.1.2:1002<->pptp2

Answer 1

Change the default action to DROP, discard the drop rule.

Answer 2

Here is an approximate script with comments to the commands:

#!/bin/bash
export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

# сбрасываем правила, очищаем цепочки
iptables -F
iptables -X

# настраиваем политики по умолчанию
iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -P OUTPUT ACCEPT

#
iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT

# LOOPBACK
iptables -A INPUT -i lo -j ACCEPT

# ICMP
iptables -A INPUT -p icmp -j ACCEPT

# если порты для tcp
iptables -A INPUT -p tcp -m multiport --dports 221,10000,2302 -m state --state NEW -j ACCEPT

# если порты для udp
iptables -A INPUT -p udp -m multiport --dports 221,10000,2302 -j ACCEPT

exit 0

The point is that we make the default policies DROP for the INPUT and FORWARD chains, and then we add the permissions we need.