2001:1248:8900::/40 - INA2
inetnum: 2001:1248::/32 status: allocated aut-num: N/A owner: Alestra, S. de R.L. de C.V. ownerid: MX-ALES-LACNIC responsible: Pedro Armando Abdo Cantú address: AV LAZARO CARDENAS #2321PTE PISO 10, 2321, RESIDENCIAL SAN AGUSTIN address: 66260 - SAN PEDRO GARZA GARCIA - NL country: MX phone: +52 81 87486201  owner-c: INA2 tech-c: INA2 abuse-c: INA2 created: 20080108 changed: 20080108 nic-hdl: INA2 person: Inet Administrator e-mail: inetadmin@ALESTRA.NET.MX address: Ave. Eugenio Clariond Garza, 175, Cuauhtemoc address: 66450 - San Nicolas de los Garza - NL country: MX phone: +52 81 87486201  created: 20030206 changed: 20110704
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.