CCDA: Cisco Certified Design Associate Study Guide, 2nd Edition (640-861)

A shared connection between a LAN and a larger system, such as a mainframe computer or a large packet-switching network, whose communications protocols are different. Usually slower than a bridge or router, a gateway is a combination of hardware and software with its own processor and memory used to perform protocol conversions.

Get Nearest Server: On an IPX network, a request packet sent by a customer for determining the location of the nearest active server of a given type. An IPX network client launches a GNS request to get either a direct answer from a connected server or a response from a router disclosing the location of the service on the internetwork to the GNS. GNS is part of IPX and SAP. See also: IPX and SAP.

Generic Routing Encapsulation: A tunneling protocol created by Cisco with the capacity for encapsulating a wide variety of protocol packet types inside IP tunnels, thereby generating a virtual point-to-point connection to Cisco routers across an IP network at remote points. IP tunneling using GRE permits network expansion across a single-protocol backbone environment by linking multiprotocol subnetworks in a single-protocol backbone environment.

The unused frequency area found between two communications channels, furnishing the space necessary to avoid interference between the two.