Listener do not forward dns query to internal name server

Dear All

 

I have 2 ISP connect to F5 LC, (ISP-1 and ISP-2)

 

I have problem with one of my Listener in ISP-2, it's Virtual Server can not forward dns query to it's default Pool.

 

I add new Listener (TCP and UDP), with new IP address, (103.247.226.158) and enable it on ISP-2 VLAN.

 

Default VS create for this Listener, and i add Default Pool with Pool member internal name server IP address (192.168.1.11), in this VS

 

The configuration for Listener,VS, and Pool are exactly same with ISP-1.

 

If we do link failover test (ISP-1 offline and ISP-2 online), we can not query our ns record from internet

 

But, it work fine if ISP-1 on and ISP-2 off

 

We done some tcpdump packet capture, in F5 LC and name server while only ISP-1 are online

 

We can see dns request packet in F5 ISP-1 interface, but can not see it in name server interface.

 

We test it with change with other protocol (SSH and FTP ) in this VS, and we can connect to those service.

 

Is there any issue that we missed here ? Please kindly help