AS11915 TPx Communications
2604:5d00:2000::/36 - TELWEST-V6-1
V6NetHandle: NET6-2604-5D00-1 OrgID: UTC-68 Parent: NET6-2600-1 NetName: TELWEST-V6-1 NetRange: 2604:5D00:: - 2604:5D00:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF NetType: allocation RegDate: 2011-04-08 Updated: 2014-09-03 AbuseHandle: ATR4-ARIN Source: ARIN OrgID: UTC-68 OrgName: TPx Communications CanAllocate: Street: 515 S. Flower St. 47th Floor City: Los Angeles State/Prov: CA Country: US PostalCode: 90071 RegDate: 2014-01-21 Updated: 2017-05-10 OrgAbuseHandle: ATR4-ARIN OrgAdminHandle: IPENG24-ARIN OrgTechHandle: ZT119-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.