Servidores DNS Principal (mname) y Secundario (rname)
host: paes.shibaura-it.ac.jp
class: IN
ttl: 28800
type: SOA
mname: ns0.shibaura-it.ac.jp
rname: postmaster.shibaura-it.ac.jp
serial: 2018061105
refresh: 3600
retry: 900
expire: 604800
minimum-ttl: 3600