In Direct Access nslookup unknown

Remove ::1 from your preferred dns server entry under network adapter settings and enter primary DNS server's ipv4 address there and try again.

Hope this help.

Check your network adapters DNS configuration, it seems you have set some dns server that is not responding as primary DNS.

You can check this by running "ipconfig /all" and under "Local area connection" (usually) check entries under "DNS servers".

After seeing the details you provided , it seems that ::1 is entered in preferred DNS Server , which is the IPv6 representation of what's known as 127.0.0.1 in IPv4.
And when you do nslookup it is pointing to 'unknown' as AAAA/PTR record is missing from DNS for ipv6 address.

extended info in nslookup suggests that ipv4 record for your DC is working fine on your network.

So, If you are not using ipv6 you can safely remove this from your preferred dns server's entry.
For removing it see my first comment.

thanks all
@Naveen Joshi    but i think ipv6 required for Direct Access ?

thanks all
@Uros Gaber  this is my ipconfig /all

PS C:\Users\Administrator> ipconfig /all

Windows IP Configuration

   Host Name . . . . . . . . . . . . : DC
   Primary Dns Suffix  . . . . . . . : domain.net
   Node Type . . . . . . . . . . . . : Hybrid
   IP Routing Enabled. . . . . . . . : No
   WINS Proxy Enabled. . . . . . . . : No
   DNS Suffix Search List. . . . . . : domain.net

Ethernet adapter Ethernet0:

   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Intel(R) 82574L Gigabit Network Connection
   Physical Address. . . . . . . . . : 00-0C-29-03-EE-61
   DHCP Enabled. . . . . . . . . . . : No
   Autoconfiguration Enabled . . . . : Yes
   Link-local IPv6 Address . . . . . : fe80::6122:88a0:197:1189%12(Preferred)
   IPv4 Address. . . . . . . . . . . : 192.168.1.100(Preferred)
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . :
   DHCPv6 IAID . . . . . . . . . . . : 251661353
   DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-1E-02-C9-35-00-0C-29-90-55-22
   DNS Servers . . . . . . . . . . . : ::1
                                       192.168.1.100
   NetBIOS over Tcpip. . . . . . . . : Enabled

Tunnel adapter isatap.{A4DCD5D7-FBC9-4B07-BA0D-86F05F01B2E4}:

   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Microsoft ISATAP Adapter #2
   Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
   DHCP Enabled. . . . . . . . . . . : No
   Autoconfiguration Enabled . . . . : Yes
   IPv6 Address. . . . . . . . . . . : 2002:c4da:3d75:1:0:5efe:192.168.1.100(Preferred)
   Link-local IPv6 Address . . . . . : fe80::5efe:192.168.1.100%14(Preferred)
   Default Gateway . . . . . . . . . : fe80::5efe:192.168.1.200%14
   DNS Servers . . . . . . . . . . . : ::1
                                       192.168.1.100
   NetBIOS over Tcpip. . . . . . . . : Disabled

ok
dns check
Directory Server Diagnosis

Performing initial setup:
   Trying to find home server...
   Home Server = DC
   * Identified AD Forest.
   Done gathering initial info.

Doing initial required tests

   Testing server: Default-First-Site-Name\DC
      Starting test: Connectivity
         ......................... DC passed test Connectivity

Doing primary tests

   Testing server: Default-First-Site-Name\DC

      Starting test: DNS

         DNS Tests are running and not hung. Please wait a few minutes...
         ......................... DC passed test DNS

   Running partition tests on : ForestDnsZones

   Running partition tests on : DomainDnsZones

   Running partition tests on : Schema

   Running partition tests on : Configuration

   Running partition tests on : domain

   Running enterprise tests on : domain.net
      Starting test: DNS
         Test results for domain controllers:

            DC: DC.domain.net
            Domain: domain.net


               TEST: Forwarders/Root hints (Forw)
                  Error: Both root hints and forwarders are not configured or broken. Please make sure at least one of
                  them works.

               TEST: Records registration (RReg)
                  Network Adapter [00000010] Intel(R) 82574L Gigabit Network Connection:
                     Warning:
                     Missing AAAA record at DNS server 192.168.1.100:
                     DC.domain.net

                     Warning:
                     Missing AAAA record at DNS server 192.168.1.100:
                     gc._msdcs.domain.net

                     Warning:
                     Missing AAAA record at DNS server ::1:
                     DC.domain.net

                     Warning:
                     Missing AAAA record at DNS server ::1:
                     gc._msdcs.domain.net

               Warning: Record Registrations not found in some network adapters

         Summary of test results for DNS servers used by the above domain controllers:

            DNS server: 128.63.2.53 (h.root-servers.net.)
               1 test failure on this DNS server
               PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 128.63.2.53
            DNS server: 128.8.10.90 (d.root-servers.net.)
               1 test failure on this DNS server
               PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 128.8.10.90
            DNS server: 192.112.36.4 (g.root-servers.net.)
               1 test failure on this DNS server
               PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 192.112.36.4
            DNS server: 192.203.230.10 (e.root-servers.net.)
               1 test failure on this DNS server
               PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 192.203.230.10
            DNS server: 192.228.79.201 (b.root-servers.net.)
               1 test failure on this DNS server
               PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 192.228.79.201
            DNS server: 192.33.4.12 (c.root-servers.net.)
               1 test failure on this DNS server
               PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 192.33.4.12
            DNS server: 192.36.148.17 (i.root-servers.net.)
               1 test failure on this DNS server
               PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 192.36.148.17
            DNS server: 192.5.5.241 (f.root-servers.net.)
               1 test failure on this DNS server
               PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 192.5.5.241
            DNS server: 192.58.128.30 (j.root-servers.net.)
               1 test failure on this DNS server
               PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 192.58.128.30
            DNS server: 193.0.14.129 (k.root-servers.net.)
               1 test failure on this DNS server
               PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 193.0.14.129
            DNS server: 198.41.0.4 (a.root-servers.net.)
               1 test failure on this DNS server
               PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 198.41.0.4
            DNS server: 199.7.83.42 (l.root-servers.net.)
               1 test failure on this DNS server
               PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 199.7.83.42
            DNS server: 202.12.27.33 (m.root-servers.net.)
               1 test failure on this DNS server
               PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 202.12.27.33
         Summary of DNS test results:

                                            Auth Basc Forw Del  Dyn  RReg Ext
            _________________________________________________________________
            Domain: domain.net
               DC                           PASS PASS FAIL PASS PASS WARN n/a

         ......................... domain.net failed test DNS
PS C:\Users\Administrator>

This seems to be a ipv6 record reg issue and you'll have to add an AAAA record to resolve nslookup issue.

https://technet.microsoft.com/en-us/library/cc816775(v=ws.10).aspx

If you dont want to add. your first step would be to remove ::1 from the preferred dns . let it remain 192.168.1.100 only.

I believe it will not break  Direct Access.
FYI : http://windowsitpro.com/networking/q-it-true-directaccess-only-works-ipv6

After remove ::1 from ipv6 dns
i got this
PS C:\Users\Administrator> nslookup isatap
DNS request timed out.
    timeout was 2 seconds.
Server:  UnKnown
Address:  192.168.1.100

Name:    isatap.domain.net
Address:  192.168.1.200

I am sorry i meant 192.168.1.200 in my last comment. Do this in both the network adapters. My mistake.

yes it's working
removed  ::1
and change ipv4 dns from 192.168.1.100 to 127.0.0.1

I am glad it worked. Cheers !