$ORIGIN example.org.
@	3600 IN	SOA   sns.dns.icann.org. noc.dns.icann.org. (
        2017042745 ; serial
        7200       ; refresh (2 hours)
        3600       ; retry (1 hour)
        1209600    ; expire (2 weeks)
        3600       ; minimum (1 hour)
)

    3600 IN NS    a.iana-servers.net.
    3600 IN NS    b.iana-servers.net.

chain1   3600 IN CNAME nxdomain
nxdomain 3600 IN CNAME nxdomain.example.net.
chain2   3600 IN CNAME srvfail
srvfail  3600 IN CNAME srvfail.example.net.
chain3   3600 IN CNAME nodata
nodata   3600 IN CNAME nodata.example.net.