I'm about installing DNS Server on VPS with Centos 5.9 operating system, I have followed step by step from this website https://www.digitalocean.com/communi...er-on-centos-6
when i try to restart the service with:

service named restart there is following error:
Stopping named: [ OK ] Starting named: Error in named configuration:
/etc/named.conf:23: unknown option 'dnssec-validation' /etc/named.conf:24: expected 'trust-anchor' near ';'
any solution to solve this problem? Thank you very much.

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