CISSP (ISC)2 Certified Information Systems Security Professional Official Study Guide by Stewart James M.; Chapple Mike; Gibson Darril & Mike Chapple & Darril Gibson

Author:Stewart , James M.; Chapple, Mike; Gibson, Darril & Mike Chapple & Darril Gibson
Language: eng
Format: epub
ISBN: 9781119042754
Publisher: Wiley
Published: 2015-08-27T00:00:00+00:00

The term modem is used incorrectly on any device that does not actually perform modulation. Most modern devices labeled as modems (cable, DSL, ISDN, wireless, etc.) are routers, not modems.

Bridges A bridge is used to connect two networks together—even networks of different topologies, cabling types, and speeds—in order to connect network segments that use the same protocol. A bridge forwards traffic from one network to another. Bridges that connect networks using different transmission speeds may have a buffer to store packets until they can be forwarded to the slower network. This is known as a store-and-forward device. Bridges operate at OSI layer 2. Systems on either side of a bridge are part of the same broadcast domain but are in different collision domains.

Switches Rather than using a hub, you might consider using a switch, or intelligent hub. Switches know the addresses of the systems connected on each outbound port. Instead of repeating traffic on every outbound port, a switch repeats traffic only out of the port on which the destination is known to exist. Switches offer greater efficiency for traffic delivery, create separate collision domains, and improve the overall throughput of data. Switches can also create separate broadcast domains when used to create VLANs. In such configurations, broadcasts are allowed within a single VLAN but not allowed to cross unhindered from one VLAN to another. Switches operate primarily at OSI layer 2. When switches have additional features, such as routing, they can operate at OSI layer 3 as well (such as when routing between VLANs). Systems on either side of a switch operating at layer 2 are part of the same broadcast domain but are in different collision domains. Systems on either side of a switch operating at layer 3 are part of different broadcast domains and different collision domains. Switches are used to connect network segments that use the same protocol.

Routers Routers are used to control traffic flow on networks and are often used to connect similar networks and control traffic flow between the two. They can function using statically defined routing tables, or they can employ a dynamic routing system. There are numerous dynamic routing protocols, such as RIP, OSPF, and BGP. Routers operate at OSI layer 3. Systems on either side of a router are part of different broadcast domains and different collision domains. Routers are used to connect network segments that use the same protocol.

Brouters Brouters are combination devices comprising a router and a bridge. A brouter attempts to route first, but if that fails, it defaults to bridging. Thus, a brouter operates primarily at layer 3 but can operate at layer 2 when necessary. Systems on either side of a brouter operating at layer 3 are part of different broadcast domains and different collision domains. Systems on either side of a brouter operating at layer 2 are part of the same broadcast domain but are in different collision domains. Brouters are used to connect network segments that use the same protocol.

Gateways A gateway connects networks that are using different network protocols.

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