CompTIA® Network+ Certification Exam Notes

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About Network+ Certification: Network+ Certification is offered by CompTIA. CompTIA recommends the aspirants to pass A+ certification, but its is NOT a prerequisite. Network+ exam topics include ISO OSI model, planning, installing, and troubleshooting basic network infrastructure. The candidate will be tested primarily on Unix/Linux, Windows 9x, Windows NT, and Windows 2000 networking systems

The sections that Network+ exam covers are given below (subject to change):

Sl.No Objective Weight
1. Media and Topologies 20%

Protocols and Standards

3. Network Implementation 23%
4. Network Support 32%
Total: 100%

Points to remember:

1. The 7 layers of OSI model are:

1.The Application Layer: Application layer is responsible for identifying and establishing the availability of desired communication partner and verifying sufficient resources exist for communication. Some of the important application layer protocols are: WWW, SMTP, FTP, etc.

2.The Presentation Layer: This layer is responsible for presenting the data in standard formats. This layer is responsible for data compression, decompression, encryption, and decryption. Some Presentation Layer standards are: JPEG, MPEG, MIDI, PICT, Quick Time, TIFF.

3.The Session Layer: Session Layer is responsible for co-ordinating communication between systems/nodes.The following are some of the session layer protocols and interfaces: a) Network File System (NFS), SQL, RPC (Remote Procedure Call), X-Windows, ASP, DNA SCP.

4.The Transport Layer: The Transport Layer is responsible for multiplexing upper-layer applications, session establishment, and tearing-down of virtual circuits. This layer is responsible for flow control, to maintain data integrity. 

5.The Network Layer: There can be several paths to send a packet from a given source to a destination. The primary responsibility of Network layer is to send packets from the source network to the destination network using a pre-determined routing methods. Routers work at Network layer.

6.The Data Link Layer:

Data Link Layer is layer 2 of OSI reference model. This layer is divided into two sub-layers:

A. Logical Link Control (LLC) sub-layer.

B. Media Access Control (MAC) sub-layer.

The LLC sub-layer handles error control, flow control, framing, and MAC sub-layer addressing.

The MAC sub-layer is the lower of the two sub-layers of the Data Link layer. MAC sub-layer handles access to shared media, such a Token passing or Ethernet.

7.Physical Layer: The actual flow of signals take place through Physical layer. At Physical layer, the interface between the DTE and DCE is determined. The following are some of the standard interfaces are defined at Physical layer: EIA/TIA-232, EIA/TIA-449,V.24,V.35,X.21,G.703,HSSI (High Speed Serial Interface).

2. Internetwork IP addressing:

IP addresses are written using decimal numbers separated by decimal points. This is called dotted decimal notation of expressing IP addresses.

The different classes of IP addresses is as below:

Class Format Leading Bit pattern Network address Range Maximum networks Maximum hosts/ nodes
A N.H.H.H 0 0-126 127 16,777,214
B N.N.H.H 10 128-191 16,384 65,534
C N.N.N.H 110 192-223 2,097,152 254

- Network address of all zeros means "This network or segment".

- Network address of all 1s means " all networks", same as hexadecimal of all Fs.

- Network number 127 is reserved for loop-back tests.

- Host (Node)  address of all zeros mean "This Host (Node)".

- Host (Node) address of all 1s mean "all Hosts (Nodes) " on the specified network.

3. The range of numbers from to are used for multicast packets. This is known as Class D address range.

4. Subnetting is nothing but creating networks within a network. Subnetting allows an organization with a single IP address (Class A /ClassB /ClassC) to have multiple subnetworks, thus allowing several physical networks within the organization. 

  • Default subnet mask for Class A network:
  • Default subnet mask for Class B network:
  • Default subnet mask for Class C network:

5. is the local loop back address.  

6. In an internetwork, the number of distinct IPs' required are

1. One each per client computer

2. One each per server computer

3. One each per router interface.

For example, your network has 2 servers, 26 clients machines, and 2 router interfaces the total number of IP addresses required are 30.

7. The directed broadcast should reach all Hosts on the intended network (or subnet, if sub netted). For example, the directed broadcast address for an IP network with default subnet mask is This is arrived by putting all 1s for the host potion of the IP address.

8.Telnet, FTP, and TFTP:

Telnet is used for terminal emulation that runs programs remotely. Telnet uses TCP/IP protocol.

Telnet requires a username and password to access.

FTP (File Transfer Protocol) is a connection oriented protocol. It uses TCP/IP for file transfer. Compare this with TFTP (Trivial File Transfer Protocol) that uses UDP (Connectionless protocol). SNMP uses UDP over IP. Tracert, Ping use ICMP as their base protocol. FTP is used to transfer files.

Both FTP and Telnet are client-server protocols. Note that TCP/IP is a client server oriented protocol.

9. The port numbers used by different programs are as below:

FTP : Port #21

II. Telnet: Port #23

III. SMTP: Port #25

IV. SNMP: Port #161

It is important to know that FTP, Telnet, SMTP use TCP; whereas TFTP, SNMP use UDP.

10. SNMP is part of TCP/IP protocol suite. It allows you to monitor and manage a network from a centralized place by using SNMP Manager software. The systems or devices that provide the responses are called agents (or MIBs). An SNMP agent is any computer running SNMP agent software.

MIB stands for Management Information Base. It is part of SNMP agent database. A MIB records and stores information abut the host it is running on. An SNMP manager can request and collect information from an agent's MIB. Routers are typical MIB agents. SNMP agent generates "trap" messages that are then sent to an SNMP management console, which is a trap destination.

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