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Network devices such as routers, switches, bridges, and hubs connect computing systems and networks. They are responsible for productive network functionality, backbone support, and the proper forwarding of information to other networks. In short, without them, there would be little or no network connectivity and minimal network security at best. In order to grasp fully the network infrastructure security concepts, it is essential that you have a general understanding of how these devices work.
is a network device that is used to connect networks. They are most often used to connect LANs. A router uses packet header information in combination with a
Routers use specialized protocols such as ICMP (Internet Control Message Protocol), OSPF (Open Shortest
Routers connect different network segments. However, unlike bridges, routers do not use a computer's MAC address to forward information. Instead, a router operates at the network layer of the OSI reference model and has the ability to forward information based on a network or individual computer's TCP/IP address. This allows a router to connect entirely separate networks and filter information to the proper network or network segment. In other words, a router has the ability to send a request to a specific location without broadcasting to all of the other computer nodes on a network or network segment.
Routers are very
Here are some important points to remember concerning routers:
They provide filtering of packets and reduce broadcast storms.
They can segment networks into smaller and more manageable pieces.
They provide a network security layer between separate networks, functioning as firewalls.
They connect LAN segments that use the same or different protocols.
is a network device similar to a router that chooses certain paths or routes in a network on which to send data. A switch is not a router although a switch can contain router functionality. Most modern day switches can operate at both the Data Link and Network
Bridges are hardware devices that operate at the MAC sublayer of the OSI reference model's Data Link layer. Bridges are used to segment or separate LANs. Separating a larger network into smaller manageable segments can improve network performance and provide a way to isolate network bottlenecks.
A bridge reads the MAC hardware address that is stored in the NIC of every computer or node installed on either side of the bridge. The bridge
Bridges can provide the following services:
Reduce network traffic as a result of too many computers being attached to a network.
Connect different types of media connections such as coaxial cable and twisted pair cable.
Expand the length of a network segment.
Connect different network typologies such as Token Ring and Ethernet.
Although bridges serve their primary purpose, they are limited in their capabilities. If a destination's MAC address is not found in a bridge's internal table, the bridge will proliferate or broadcast (pass traffic) to all network segments. This can result in a broadcast
As networks grew larger, the demand for a more intelligent device that could handle more attached computer nodes and direct network traffic in more efficient manner increased. The router was technology's answer to this demand.
As mentioned earlier in this chapter, a hub is a network device that acts as a central point used to connect computers. In network terms, a hub is a simple connection device that sends all data packets to all connected systems. A basic hub operates at the Physical layer of the OSI reference model.
or just plain
is a telephone-switching system inside an enterprise that allows calls to be shared or switched to various numbers assigned within the enterprise. Callers inside of the enterprise also share external PBX lines for outbound or outside calling. A PBX offers the flexibility of inside calling
There are many types of modems available on the market today. Popular modems types include cable, wireless, Digital Subscriber Line (DSL), and analog dial-up modems.
is an abbreviation for
There are many ways your system can be attacked. Today, most systems are
You should also have a good antivirus program and make use of a personal firewall system. Other than that, once again, back up your important data!
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