We pick b.root-servers.net, one of the 13 root servers (1), and ask it about bol.navy.mil and learn that mil is delegated to six name servers (2), so we ask con2.nipr.mil where we learn that navy.mil is delegated to seven name servers, including guv10m01.mont.disa.mil (3), so we ask that one and learn that bol.navy.mil is delegated to four name servers (4), so we ask c27dnsmill01.mdc.navy.mil and get the following answer:
Bol.navy.mil is a domain controlled by two domain name servers at navy.mil. Both are on the same IP network. Incoming mail for bol.navy.mil is handled by two mail servers also at navy.mil. Both are on the same IP network.