|  | 1.3 | LAN Design
| 1.3.6 | Extended star topology
In larger networks it is not unusual to have more than one wiring closet if there are hosts that need network connectivity but are outside the 100-meter limitation for Category 5 UTP Ethernet. By creating multiple wiring closets, multiple catchment areas are created. The secondary wiring closets are referred to as Intermediate Distribution Facilities (IDF). TIA/EIA- 568-A Standard specifies that IDFs will be connected to the MDF using vertical cabling. This vertical cabling is typically fiber-optic cable because fiber-optic cable can be run longer distances. In the MDFs and IDFs the major difference is the implementation of another patch panel, which can be the vertical cross connect (VCC). This VCC is used to interconnect the various IDFs to the central MDF. Since the vertical cable lengths are typically longer than the 100-meter limit for CAT 5 UTP cable, fiber-optic cabling is normally used. Upcoming Changes in Cabling Standards Design Hint - Since the vertical cabling will be carrying all data traffic between the IDFs and MDFs, the speed of this connection should be designed to be the fast link in the network. In most cases this link should be at least 100 Mbps. Also, additional vertical cable runs should be installed to allow for future growth in the network.