TMG ISP Redudancy and DNS

Hello Experts,

actually this is the continuation of my previous question

Hello,

I have installed TMG with 3 NICs such as ISP1, ISP2 and Internal

I configured the ISP1 and ISP2 interfaces with IP addresses and default gateways and

configured internal NIC with IP address, but no  Default Gateway.

I installed DNS service on TMG and configured the forwarders pointing to ISP DNS servers.

Finally Internal NIC DNS configuration as follows

Primary : 127.0.0.1

Alternative: Internal AD DNS servers

Configured persistent routes

=============================================================
Persistent Routes:
  Network Address          Netmask             Gateway Address  Metric
         10.0.0.0               255.0.0.0                      10.1.2.1            1                  ( Internal LAN)
          1.1.1.1            255.255.255.255             192.168.5.1       2                   ( ISP1 DNS Server)
           2.2.2.2           255.255.255.255             192.168.4.2       3                    ( ISP2 DNS Server)
           0.0.0.0                 0.0.0.0                       192.168.4.2    Default
           0.0.0.0                 0.0.0.0                       192.168.5.1  Default

Suddenly I started facing a problem that web proxy client receiving a pop up Authentication Required.

I tried nslookup on TMG server for my domain domain but cannot resolved.

I would highly appreciate any help.


Thanks