Secondary Nameserver Configuration file
cache . domain-name-service.cache
primary 0.0.127.in-addr.arpa domain-name-service.local
secondary opus1.com 161.44.128.70 dns.opus1-bkp
secondary 44.161.in-addr.arpa 161.44.128.70 dns.opus1-net-bkp
161.44.128.70 = IP Address of primary nameserver for this zone