core-1.nbuilding.net has one IP number. dai.es, nxs7.com, bobcat.ca, tbelt.com, jesdor.com and at least 100 other hosts point to the same IP. nbuilding.net is a domain controlled by two nameservers at nbuilding.net themselves. They are on the same IP network. Incoming mail for nbuilding.net is handled by two mailservers having a total of three IP numbers. There are three duplicated IP numbers. Some of them are on the same IP network.