The requirement for RJ45 cross-over, or x-over, cables is dictated by the type of devices that are being connected. There are two interface types associated with networking equipment, DTE (Data Terminating Equipment) and DCE (Data Communications Equipment). DTE devices mainly consist of PC NICs and Routers. When connecting a DTE device to a DCE device, e.g., a PC to a Hub, a straight cable is required. When the two connecting devices have the same interface type, i.e., both DCE or both DTE, then a x-over cable is necessary.
Unfortunately, these examples do not constitute hard and fast rules. Some Cable Modems, especially those integrated in Set-Top Boxes, have DTE interfaces, so any PC or Router that connects to it will need a x-over cable. Also, when connecting two hubs together a x-over cable may not be necessary if one of the hubs has an uplink port. An uplink port will have a DTE type interface, so a straight cable can be used to connect to another DCE port, such as a hub port. On many hubs, one of the ports may have a port that is switchable between DCE and DTE. This function can be manual, so a switch has to be activated, or an interface can auto-detect what type of interface it needs to be.
No comments:
Post a Comment