DNS does not work if "default" interface is down

dims · Apr 29, 2017, 12:23 PM

I have 3 WANs configured:

They are all load balancing

Unfortunately, once "default" interface is dowm, DNS doesn't work anymore. I can still access sites by IP, but DNS is not available.

This is probably because of DNS forwarder, which is resolving DNS only via default interface.

How to fix this?

johnpoz · Apr 29, 2017, 1:15 PM

use the resolver and have it use 1 or all of the interfaces you would like it to be able to use..

jimp · May 1, 2017, 2:10 PM

If you are using the forwarder, or the resolver in forwarding mode, go to System > General Setup, and setup one DNS server for each WAN. So the first DNS server would use the gateway for the first WAN, second with a gateway for the second WAN, and so on.

If you are using the resolver in non-forwarding mode, then activate default gateway switching from System > Advanced, Misc.

dims · Jan 2, 2018, 11:37 AM

How can I set DNS for each WAN? It should be set by DHCP. I just don't know which DNS is for which WAN!

Of course, I know 8.8.8.8 and 8.8.4.4, but these are only 2, while I need 3.

rudger_wolvram · Jan 3, 2018, 7:02 PM

I'm using the forwarder and have mine set up this way (I also have IPv6 set up) and was having the same problem until I added the last 2 entries.
Under System/General Setup on the DNS server settings I have 6 entries.

2001:4860:4860::8888 WAN_DHCP6 (google IPv6)
2001:4860:4860::8844 WAN_DHCP6 (google IPv6)
208.67.222.222 WAN1_DHCP (openDNS)
208.67.220.220 WAN1_DHCP (openDNS)
8.8.8.8 WAN2_DHCP (Google)
8.8.4.4 WAN2_DHCP (Google)

If I failover to WAN2 it will use those two google DNS servers, if I am running normally, it uses openDNS.

Note, I don't know if I can have duplicate DNS server IPs with different interfaces. I've never tried.