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 A+ Essentials (220-801) Cram Notes


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2. Networking

   2.1 Identify types of network cables and connectors

1. Shielded cables usually comprise of one or two insulated wires that are surrounded by an aluminum Mylar foil or a woven braided shield. The foiled shield of the cable ensures better signal transmission by eliminating irregular power frequency and external radio interference. Mostly, power cables which carry high-voltage of electricity are shielded for greater protection and better electric transmission. Shielded cables exhibit better interference rejection characteristics compared to unshielded cables.

2. The IEEE 1394 interface is a serial bus interface standard for high-speed communications frequently used by personal computers, as well as in digital audio, and digital video, The interface is also known by the brand names of FireWire (Apple), i.LINK (Sony), and Lynx (Texas Instruments).

3. A punch down tool, also called a punch down tool is used widely by network technicians. It is used for inserting wire into insulation-displacement connectors on punch down blocks or patch panels.

4. A crimping tool is a tool designed to crimp or connect a connector to the end of a cable. For example, network cables and phone cables are created using a crimping tool to connect the RJ-45 and RJ-11 connectors to the end of the cable.

5. RG-6 may be used for both analog and digital television transmission.

   2.2 Categorize characteristics of connectors and cabling

1. CAT3: This standard was used in 90's for homes and offices. It can transmit data up to 10Mbps with a possible bandwidth of 16MHz

2. CAT5: It uses either the 10BASE-T or 100BASE-T standard for data transmission Using two cable pairs to signal over copper wire. It provides a minimum of 100MHz of bandwidth.

3. CAT5e: It uses four pairs of copper wire. In addition, the wire pairs are twisted more tightly and are sheathed in heavy-duty shielding to eliminate crosstalk. It is used for 1000BASE-T networks, which carry data at a rate of 1 Gbps.

4. CAT6: It can transmit data up to 10Gbps, has a minimum of 250MHz of bandwidth and specifies cable lengths up to 100 meters with 10/100/1000Mbps transfer, along with 10Gbps over shorter distances. It is made up of four twisted pairs of copper wire, an longitudinal separator separates each of the four pairs of wires from each other

5. CAT 6a: It can operate at a frequency of up to 750 MHz and is even less susceptible to interference and crosstalk CAT6a is the preferred cable for 10GBASE-T Ethernet  

   2.3 Explain properties and characteristics of TCP/IP

   1. TCP/IP

  • TCP/IP is the medium of transport when your are accessing the Internet.

  • Some important TCP/IP port numbers are as given below:

1. FTP: 21, stands for File Transfer Protocol  is a client server protocol Your Windows machine, running FTP client can communicate with the Unix Server running FTP server daemon, and transfer files to and from your computer.

2. Telnet: 23, stands for Telnetting from a remote terminal to a Telnet Server

3. SMTP: 25, stands for Simple Mail Transfer Protocol

4. HTTP/WWW: 80, stands for Hyper Text Transfer Protocol

5. POP3: 110, stands for Post Office Protocol

6. HTTPS: 443, stands for HTTP Secure

  • TCP/IP is the protocol used when you are Telnetting to a remote host. HTTP is used for accessing the World Wide Web services.

  • Some of the important commands useful in trouble shooting TCP/IP networks are:

  • Ipconfig: Displays TCP/IP configuration values, including IP address, subnet mask, and default gateway. Available options with ipconfig command are given below:

 /?               Display this help message

 /all             Display full configuration information.

 /release         Release the IPv4 address for the specified adapter.

/release6        Release the IPv6 address for the specified adapter.

 /renew           Renew the IPv4 address for the specified adapter.

/renew6          Renew the IPv6 address for the specified adapter.

/flushdns        Purges the DNS Resolver cache.

 /registerdns     Refreshes all DHCP leases and re-registers DNS names

/displaydns      Display the contents of the DNS Resolver Cache.

 /showclassid     Displays all the dhcp class IDs allowed for adapter.

 /setclassid      Modifies the dhcp class id.

 /showclassid6    Displays all the IPv6 DHCP class IDs allowed for adapter

/setclassid6     Modifies the IPv6 DHCP class id.

  • nslookup provides the IP address of the remote computer after querying the dns server for the IP config information.

  • Ping: This command can be used to verify whether the target ip address or host name is present. You need to specify the target IP address or host name. You can ping the loop back address at A response ensures that the TCP/IP stack is installed properly on your computer.

  • Route: Displays and manipulates route information.

  • Tracert: Determines the route packets take to reach the specified destination.

2. SMTP  is used to upload mail to the mail server. POP3 is used for downloading mail from a mail server to a client machine running POP3 client.

3. Both PPP and SLIP can be used for dial up connections. However, SLIP can't be used where the IP address need to be assigned dynamically. The advantage of PPP is multi protocol support, that it can support TCP/IP, IPX, AppleTalk etc. SLIP can support only TCP/IP and IP addresses need to be assigned manually.

4. WINS server resolves the NetBIOS names to IP addresses. A Windows network running TCP/IP need to be configured with WINS (or LMHOSTS file on each computer) for NetBIOS name resolution.

5. HOSTS file and DNS (Domain Name Server) are used for resolving FQDNs (Fully Qualified Domain Names) to IP addresses.

6. Networking utilities

a. NBTSTAT: This utility displays current NetBIOS over TCP/IP connections, and display NetBIOS name cache.

b. NETSTAT: Displays protocol statistics and current TCP/IP connections since the server was last booted.

c. TRACERT: Used to determine which route a packet takes to reach its destination from source.

d. IPCONFIG: Used to display Windows IP configuration information.

e. NSLOOKUP: This utility enables users to interact with a DNS server and display resource records.

f. ROUTE: Used to display and edit static routing tables.

g. Netsh is a command-line scripting utility that allows us to, either locally or remotely, display or modify the network configuration of a computer. Netsh also provides a scripting feature that allows us to run a group of commands in batch mode against a specified computer.

7. APIPA stands for Automatic Private IP Addressing. A feature of Microsoft Windows, APIPA is a DHCP failover mechanism. With APIPA, DHCP clients can obtain IP addresses when DHCP servers are nonfunctional. APIPA exists in all popular versions of Windows except Windows NT. When a DHCP server fails, APIPA allocates IP addresses in the private range to Clients verify their address is unique on the network using ARP. When the DHCP server is again able to service requests, clients update their addresses automatically.

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