CentOS 5.3 upgrades to CentOS 5.4 causing named or BIND DNS server to producing a lot of “network unreachable resolving … ” errors in system logs /var/log/messages causing the log file increasing in size tremendously on busy system.

Root Caused of the issue :

According to the change log of BIND for CentOS 5.4 updates (bind-chroot-9.3.6-4.P1.el5_4.1) , the latest BIND DNS server as default is now enable for IPV6 DNS resolving. Any DNS query will caused the program to also resolved IPV6 IP although the host server or client is not IPV6 enable or capable

Workaround / Solution :

Disable the IPV6 in BIND. For CentOS 5.4, edit the /etc/sysconfig/named file and add the following options into the BIND startup

OPTIONS=”-4″

This will cause the BIND server to only resolve or use IPV4 and disable IPV6 support. Save the file and restart BIND server.

That will stop those annoying error message.

Créditos : http://www.hafizonline.net/blog/?p=164