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ZyWall USG50 DNS Problem

I just received my USG50 and I am experiencing a very odd problem.
I have two ISPs, T1 + Cable.
T1 is Static IP, Static DNS, Cable is Dynamic.

I set up two interfaces and set up rounded robin, with max bandwidth 3mbps for T1 and 15mbps for Cable.

When I remove T1 connection and use Cable Only, connection chokes because I assume it is trying to send requests through T1's DNS.

So I thought there could be a way to specify which WAN should use which DNS, I set it up as following:

» ··· 53523216

It still does not help.

Any suggestions?
When I use both interfaces it seems to work, but I am afraid if our T1 is down or overloaded, we will face DNS problems.


I have to bring this thread back up, today our T1 line went down, and while we had connection through Cable, it was very laggy mainly because the USG50 was still trying to use the T1's DNS servers to resolve addresses. I could not find any way to disable or link DNS to an interface, I had to delete T1's DNS servers now it works fine.
Is there anyway to fix this properly? It is a huge pain because when T1 is back up I have to go back in and enter T1's DNS servers back in, and this defeats the purpose of failover switch.

Sarcastic Llama? Naw, Just Acerbic
Dartmouth, NS
Good questions!!
I checked my dns settings in system and I use opendns servers.
I do have my secondary ISP DNS server listed as well.

Domain Zone Forwader (system-dns) is probably the place to start reading the UG and the firmware help notes.
Ain't nuthin but the blues! "Albert Collins".
Leave your troubles at the door! "Pepe Peregil" De Sevilla. Just Don't Wifi without WPA, "Yul Brenner"

LlamaWorks Equipment


It's hard to tell if this is dns-only or if the USG50 is actually trying to send some data over the other connection as well. I strongly believe it is DNS only since deleting DNS from T1 helped.
I am very sure that there is a setting somewhere in the control panel, but the way USG is set up, it is so very detailed where you have to make changes in multiple locations instead of just one main panel.


Brighton, TN

2 edits
FWIW, I don't think your issue is DNS (depending on circumstances).

Hmmm, well after reading your post again, maybe it is...let me explain...

I have another thread here where I am experiencing momentary internet disconnects (on a USG50 also), and I'm trying to figure out what the hell is going on......anyway, I turned on some logging, and when the connection drops, there is an entry in the log that says "wan1 ping check is failed. Zone Forwarder removes DNS servers from records". In my case, my IP is dynamic, so it pulls its dns servers when it gets its ip on the wan interface. So, if the interface goes down, it removes those DNS records.

Another option would be to use public DNS servers (I also use OpenDNS), that way, it doesn't matter what interface goes down, it won't be relying on either DNS servers for either ISP.

I hope this helps in some way...


-EDIT- I just checked my USG, and in system-dns, whether you specify an ISP provided DNS or a public (static) DNS, in either case you specify which WAN interface the DNS is used on. Also, as you can see from my log, when an interface goes down, the DNS related to that particular interface is removed.