Summary
movil2.bt.es has two IP numbers. They are on different IP networks.
ns.rediris.es and
sun.rediris.es point to the same IP.
bt.es is a domain controlled by three nameservers. Two of them are on the same IP network. Incoming mail for
bt.es is handled by two mailservers at
bt.es themselves. They are on the same IP network.
movil2.bt.es is hosted on two servers in Spain.