Hi

Am using a 2820vn with 3.3.0 firmware.

I have 2 adsl connections, 1 (ISP 1) plugged directly into DSL on the 2820 and the other (ISP 2) via WAN2 and a draytek 110 modem.

They are connected to different ISP's.

The connections work fine most of the time but then I noticed DNS timeouts from time to time.

By watching the NAT Session table on the router I determined that sometimes the router would query the DNS of ISP 1 but over the ISP 2 connection which obvisouly will not work!

Apart from using something like opendns is this desired behaviour? Surely WAN 1 should only use ISP 1 DNS Servers and WAN 2 only use ISP 2 DNS Servers?

Cheers

Paul

Sorry to reply to my own post, but just wanted to check, does no-one else see this behaviour?

To replicate I just do a nslookup from a client that points to the 2820 for its DNS resolving, I then watch the NAT session table whilst I try to resolve various random addresses, whenever I get a DNS timeout the NAT session table shows an outbound port 53 connection to the wrong DNS server - both connections are up and stable?

To me it seems a pretty big flaw but im beginning to wonder if its something unique to my setup if no-one else is seeing it.

Paul

it has been mentioned before on this forum. as you've discovered, most people use opendns etc to overcome the problem.
yes, it's not right.

Is it not possible to use the "load Balance" configuration to send requests for IP1 DNS destination through WAN1 and for IP2 DNS destinations through WAN2?

... be aware that I am a complete noob at this though....

We have a similar setup, the solution I've found is to set up a load balance policy to route the DNS packets to the correct server on each connection.
On the 2820 you can find it in WAN > Load balance policy, then set up a rule as follows:

Set the protocol to UDP (or both), set the connection to WAN1 depending, leave the source IP and ports blank, set the destination IP as the DNS server for connection 1 with the destination port as 53 (this is the default port for DNS traffic). Set it to NOT automatically fail over to the other connection and don't forget to select the Enable checkbox.

Now do the same for the second connection's DNS server(s)

You can also use the same method for any other traffic you only want to go over one connection.

You may well also need to 'load balance' https (port 443) traffic to go through a specific WAN interface because if you are switched by the router from WAN1 to WAN2 mid-session, the remote end will probably throw a hissy fit and kick you.