Nslookup Error [root@ns1 named]# nslookup grac4-scan.grid4.example.com ;; connection timed out; trying next origin Server: 192.168.5.50 Address: 192.168.5.50#53 ** server can't find grac4-scan.grid4.example.com: NXDOMAIN /var/log/messages of the BIND Nameserver contains a lot of IPV6 related errors using GNS host : GNSTESTHOST .. Jun 24 15:19:08 ns1 named[7529]: error (network unreachable) resolving 'GNSTESTHOST.grid4.example.com.de.oracle.com/AAAA/IN': 202.12.27.33#53 Jun 24 15:19:08 ns1 named[7529]: error (network unreachable) resolving 'GNSTESTHOST.grid4.example.com.de.oracle.com/A/IN': 2001:503:ba3e::2:30#53 Jun 24 15:19:08 ns1 named[7529]: error (network unreachable) resolving 'GNSTESTHOST.grid4.example.com.de.oracle.com/AAAA/IN': 2001:503:ba3e::2:30#53 Jun 24 15:19:08 ns1 named[7529]: error (network unreachable) resolving 'GNSTESTHOST.grid4.example.com.de.oracle.com/A/IN': 2001:500:2::c#53 Jun 24 15:19:08 ns1 named[7529]: error (network unreachable) resolving 'GNSTESTHOST.grid4.example.com.de.oracle.com/AAAA/IN': 2001:500:2::c#53 Jun 24 15:19:08 ns1 named[7529]: error (network unreachable) resolving 'GNSTESTHOST.grid4.example.com.de.oracle.com/A/IN': 2001:500:2d::d#53 Jun 24 15:19:08 ns1 named[7529]: error (network unreachable) resolving 'GNSTESTHOST.grid4.example.com.de.oracle.com/AAAA/IN': 2001:500:2d::d#53 .... Jun 24 15:19:08 ns1 named[7529]: error (network unreachable) resolving 'GNSTESTHOST.grid4.example.com.de.oracle.com/A/IN': 2001:dc3::35#53 Jun 24 15:19:08 ns1 named[7529]: error (network unreachable) resolving 'GNSTESTHOST.grid4.example.com.de.oracle.com/AAAA/IN': 2001:dc3::35#53 Jun 24 15:19:18 ns1 named[7529]: error (network unreachable) resolving 'GNSTESTHOST.grid4.example.com.de.oracle.com/A/IN': 2001:502:f3ff::64#53 -> All the failed IVPV6 requests add a delay for the request and leads to the nslookup Timeout -> As our network can't handle IPV6 we need to disable IVP6. FIX : Disable ipv6 on CentOS 6/7 / RHEL 6/7 Edit the /etc/sysctl.conf. # vi /etc/sysctl.conf Put the following entry to disable IPv6 for all adapter. net.ipv6.conf.all.disable_ipv6 = 1 [root@ns1 named]# ifconfig eth1 eth1 Link encap:Ethernet HWaddr 08:00:27:2B:5E:DD inet addr:192.168.5.50 Bcast:192.168.5.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:2171 errors:0 dropped:0 overruns:0 frame:0 TX packets:1461 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:159819 (156.0 KiB) TX bytes:185391 (181.0 KiB) -> No IPV6 reference anymore After disabling IPV6 only very less named records should be logged in /var/log/messages : Jun 24 15:49:07 ns1 named[3152]: zone 2.168.192.in-addr.arpa/IN: sending notifies (serial 2009011201) Jun 24 15:49:07 ns1 named[3152]: zone 5.168.192.in-addr.arpa/IN: sending notifies (serial 2009011201) Jun 24 15:50:45 ns1 named[3152]: error (FORMERR) resolving 'GNSTESTHOST.grid4.example.com/AAAA/IN': 192.168.5.54#53 Jun 24 16:00:48 ns1 named[3152]: error (FORMERR) resolving 'GNSTESTHOST.grid4.example.com/AAAA/IN': 192.168.5.54#53 Jun 24 16:10:50 ns1 named[3152]: error (FORMERR) resolving 'GNSTESTHOST.grid4.example.com/AAAA/IN': 192.168.5.54#53 Jun 24 16:16:52 ns1 named[3152]: client 192.168.5.101#29873: RFC 1918 response from Internet for 5.1.168.192.in-addr.arpa ... Nslookup should now work fine [root@ns1 log]# nslookup grac4-scan.grid4.example.com Server: 192.168.5.50 Address: 192.168.5.50#53 Non-authoritative answer: Name: grac4-scan.grid4.example.com Address: 192.168.5.200 Name: grac4-scan.grid4.example.com Address: 192.168.5.165 Name: grac4-scan.grid4.example.com Address: 192.168.5.166