SIP device behind OpenWrt router/firewall

Ahoy friends.
I've moved to an OpenWRT device, and i'm extremely satisfied. There was no other choise for me, because i've got 2 WAN links, and i wanted to have load balancing using mwan3.
All the time before i have been using a Fritz! 7490 router also for my DECT devices. I got SIP numbers registered in there, and my Fritz! 7490 is now acting as an IP-Client. Unfortunately it's not possible to get the SIP phone numbers registered now, because of "DNS failure". According to the router's log.
How do i have to proceed in order to get SIP working behind the OpenWRT firewall? Is NAT the way i have to go? Or port forwardings? Thanks in advance!

Which ISP? I am an O2 customer in germany, and I had to resort configuring their DNS servers into my SIP basestation (a n old gigaset) as they round-robin the SIP-servers and only deliver their IP addresses directly from their DNS-servers... Security by obscurity newer gets old ,)
Maybe your ISP might be doing something similar and maybe you opted for a different DSNS source than your ISP?


I think that's the same problem i have. My ISP is NetCologne, and the SIP proxy But i'm not able to resolve it, using my default DNS, so i might use something else like you said.


That is a better solution, than my forcing the SIP base to use the ISP's DNS servers as I now need to mind to different DNS configurations.

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Can't you resolve the SRV record? 3560 IN SRV 20 1 5060

And the A record? 3600 IN A


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