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Chapter Overview

Network devices

Hubs

Broadcast For star topology Same as a repeater Operate at the physical layer

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Modems

Short for Modulator/Demodulator Digital to analog then to digital

Phone (POTS – plain old telephone service)

DSL (Digital Subscriber Line) Allow network signals to pass over phone

lines Cable

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Network Interface Card (NIC)

Supports a protocol Convert parallel digitals signal to serial

analog signal and serial analog signal to parallel digital signals

Mostly built in now Has LEDs to show if the line is live and

transmitting data Transceiver – converting signals from, say

100Base0TX to 100Base0FX

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An (Old) Combination Ethernet NIC

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A BNC Connector with a T Attached

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An Ethernet NIC with an RJ-45 Jack

Bridge

Connect similar network segment together

Break collision domains Designed for the bus topology

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Switch

Point to point communication Segment the message in Switch-hub

setting – function like a bridge Know MAC address

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Wireless Access Point (AP)

Support 802.11a/b/g/n

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Understanding Routing A router is a system connected to two or more

networks that forwards packets from one network to another.

Routers operate at the network layer, sometimes referred as layer 3, of the Open Systems Interconnection (OSI) reference model.

Routers can connect networks running different data-link layer protocols and different network media.

Large internetworks often have redundant routers, providing multiple routes to a destination.

Routers select the most efficient route to each destination.

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Redundant Routers

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Router Products

The Microsoft Windows 2000~2012, Microsoft Windows NT, and Novell NetWare operating systems include routing capability.

A stand-alone router is a hardware device that is essentially a special-purpose computer (with CPU, RAM, HD, and NICs).

More in later chapters

Firewall

Can be software or hardware It separates Intranet from Internet

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DHCP

Addresses the shortcomings of RARP and BOOTP (two other protocols)

Dynamically allocates IP addresses from a pool

Reclaims unused addresses Prevents IP address duplication

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DHCP Address Allocation Types

Manual allocation Static IP address, DHCP is only good for lookups

Automatic allocation Same IP address, assigned by DHCP server

Dynamic allocation (Next page)

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Dynamic Allocation

The DHCP server leases to the client an IP address chosen from a pool.

The client must periodically renew the lease address.

Unrenewed lease addresses are returned to the pool.

Dynamic allocation allows you to add, remove, and relocate computers.

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The IP Address Leasing Process The address assignment process is the same

for all of the allocation methods. Clients using manual or automatic allocation

receive no further communication after the address assignment.

Clients using dynamic allocation lease IP addresses for a time interval specified by the server.

The client must renew the lease on a regular basis to continue using it.

DHCP address leases are typically measured in days.

If addresses are in short supply, a shorter lease interval is warranted.

If computers are rarely moved to other subnets, longer lease intervals reduce the DHCP traffic.

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Others

Multilayer Switch – level 3 switch Content Switch/Web Switch

Operate at even higher level than 3 Rout to different web server based on requesting

content Intrusion Detection or Prevention System

Really? Firmware version of software

Load Balancer DNS Server (Domain Name Service)

Convert IP address to domain name back Proxy Server

Useful URL

http://www.tcpipguide.com/free/

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