Servidores DNS Principal (mname) y Secundario (rname)
host: american-capital-agencycorp.net
class: IN
ttl: 1800
type: SOA
mname: anna.ns.cloudflare.com
rname: dns.cloudflare.com
serial: 2373441020
refresh: 10000
retry: 2400
expire: 604800
minimum-ttl: 1800