2620:1fb::/36 - 24-HOUR-FITNESS-USA
V6NetHandle: NET6-2620-1FB-1 OrgID: 2HF-1 Parent: NET6-2620-1 NetName: 24-HOUR-FITNESS-USA NetRange: 2620:1FB:: - 2620:1FB:FFF:FFFF:FFFF:FFFF:FFFF:FFFF NetType: assignment OriginAS: 12061 RegDate: 2014-04-24 Updated: 2014-04-24 Source: ARIN OrgID: 2HF-1 OrgName: 24 Hour Fitness USA, Inc. CanAllocate: Street: 2234 Rutherford Rd. City: Carlsbad State/Prov: CA Country: US PostalCode: 92008 RegDate: 1999-03-15 Updated: 2014-04-25 OrgTechHandle: LEVIN3-ARIN OrgNOCHandle: LEVIN3-ARIN OrgAbuseHandle: LEVIN3-ARIN OrgNOCHandle: ICS4-ARIN OrgTechHandle: RAINE16-ARIN OrgAbuseHandle: RAINE16-ARIN OrgTechHandle: ICS4-ARIN OrgNOCHandle: RAINE16-ARIN OrgAdminHandle: ICS4-ARIN OrgAbuseHandle: ICS4-ARIN Source: ARIN
IP address ranges, or netblocks, are groups of related IP addresses. They are usually represented as a base IP address, followed by a slash, and then a netmask which represents how many IP addresses are contained within the netblock. This format is known as CIDR. You'll also sometimes see netblocks given as a start ip address, and an end ip address, or an ip address range.
Traffic works its way around the internet based on the routing table, which contains a list of networks and their associated netblocks.