Solved: "Recursive routing detected" loop issue using OpenVPN on DD-WRT

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Hello forum!

I've used OpenVPN on Asus RT-N18U running DD-WRT over a year now. I made files up.sh to start and dn.sh to stop OpenVPN to get rid of GUI and later on to run them via ssh from lan. OpenVPN version got updated to 2.4 and I made the necessary changes to conf file and scripts. It ran without issues couple of months. However, last Thursday my VPN connection went down while I was just browsing the interwebs. OpenVPN log was filled with messages: Recursive routing detected, drop tun packet to [AF_INET]62.102.148.132:443. There's no difference if I set up OpenVPN via GUI or use only my scripts. I've tried both UDP and TCP protocols but the issue persists. Outcome is always the same. Since then I've contacted AirVPN support as I cannot fix this by myself. I don't have the skills for that and I've tried my everything. As you may notice I feel desperate.

 

EDIT: Here was a zip-file including kernel and ip routing tables, scripts, openvpn.conf file and OpenVPN log. I've censored my IP-address and tun1 IP from the files.

 

All I found out is that the router for some reason removes line 62.102.148.132 via 84.xx.xx.xx dev vlan2 from routing table. You can see the difference between before-error_ip-route.txt. and after-error_ip-route.txt. DD-WRT seems to think that the fastest route outside is only via tun1 as VPN endpoint IP is in the same location as tun1 IP-address. Just a guess, might be totally wrong. Then it removes the previously mentioned routing rule and creates a loop. If I use allow-recursive-routing option in OpenVPN configuration, after a while log begins to spam "UDP messages too big" or something like that.

 

I hadn't done any changes to DD-WRT settings, configuration files or script files. Recursive routing just popped up from no where. Router is being used as a gateway and WiFi AP only. All I've done is I moved to a new apartment which has different IP-address provided by the same ISP. That might not affect anything, just FYI.  

 

I really hope someone could help me with this. Thanks.

 

 

Update:

 

Turns out my ISP assings new IP-address every 20 minutes and almost every service on DD-WRT restarts which makes everything kind of frustrating to config...