Linux multihome openvpn
Split DSL local and international traffic on different accounts.
Note: PSK only supports single tunnel, need to use cert's for multi client. https://community.openvpn.net/openvpn/wiki/GettingStartedwithOVPN
Setup of OpenVpn on multihome box.
Problem is Openvpn answers udp packets back using default Gw, and selects different ip than incoming ip.
Options:
OpenVpn: Bind to all interfaces.
- Linux selects int/ip based on routing. Local gen packets select int before mangle can replace fwmark.
OpenVpn: Bind to lo:127.0.0.2, use nat to nat incoming on udp:1194 to 127.0.0.2.
Kernel bug ? Still selecting wrong source
OpenVpn: Multiple instances each bound to specific ext ip.
- WORKS! but need separate subnet for each instance, thus client ip changes when re-connects.
Setup OpenVpn to add host routes as they activate ?
OpenVpn: Solution - :-) bind to a real interface
Solution
bind to single ip real inside int. (loop does not work ? bug -Maybe need sysctl -w net.ipv4.conf.all.route_localnet=1 ) - Nat external to real int.
- Tested can connect to any of the external ip's
- My guesse as to why it works is that the packets are seen as being routed out ? e.g. bash script to setup nat.
#!/bin/bash iplist_FWext="e1=196.1.1.1 e2=196.2.1.1 e3=196.3.1.1" iphost_FWint="10.0.0.1" for i in ${iplist_FWext}; do fw_ip=${i##*=} fw_int=${i%%=*} nat to-destination "${iphost_FWint}" dport 1194 proto udp dst "${fw_ip}" done;