push "dhcp-option DOMAIN yourdomain.local"
push "dhcp-option DNS X.X.X.X"

push "redirect-private bypass-dns"

zone "local" IN {
    type master;
    allow-update { none; };
    notify no;
    file "/etc/bind/local.zone";
};

$TTL 600
@       IN      SOA     dns.local. root.local. (
                        2018061001      ; serial
                        12h             ; refresh
                        1h              ; retry
                        2w              ; expire
                        1h              ; minimum
                        )
;
                NS      ns              ; Inet Address of name                         server
                MX      10 mail.local.  ; Primary Mail Exchanger
                MX      20 mail.local.  ; Secondary Mail Exchanger
localhost       IN      A       127.0.0.1
dns             IN      A       172.31.0.1
ns              IN      A       172.31.0.1
mail            IN      A       172.31.0.1
client100       IN      A       172.31.0.100
client101       IN      A       172.31.0.101