$TTL 600
@ IN SOA serverd.lab.example.com. root.example.com. 2025021201 3H 15M 1W 60
  IN NS serverb.lab.example.com.
  IN NS serverc.lab.example.com.

servera IN A 192.168.0.10
serverb IN A 192.168.0.11
serverc IN A 192.168.0.12
serverd IN A 192.168.0.13