CCNA study notes on Internetwork IP addressing

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About CCNA Exam: CCNA exam tests you in the areas of simple LAN/WAN switching, Cisco IOS, and routing. Topics include TCP/IP model of internetworking, configuring, and troubleshooting some of the most widely used Cisco switches and routers. Also, CCNA is foundation exam for CCNP (Cisco Certified Networking Professional). The exam notes is a brief review of important points that help in quick review of key points.

1. 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

2. The range of numbers from 224.0.0.0 to 239.255.255.255 are used for multicast packets. This is known as Class D address range.

3. 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.

4. How to maximize the number of subnets for a given number of hosts:

Let us take a network ID of 168.8.0.0, and find the maximum number of possible subnets and the corresponding subnet mask that can accommodate at least 500 hosts. The steps involved are outlined below:

5. How to maximize the number of hosts for a given number of subnets:

Determining the subnet mask that allows maximum number of hosts:

Let us consider an IP address 196.202.56.0 with four subnets and maximize the number of host for the given subnets. The steps involved are as below:

6. 127.0.0.1 is the local loop back address.

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

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

8. Finding the number of Hosts and subnets available for a given subnet mask: For example, let us find the number of hosts and subnets available for an IP 156.233.42.56 with a subnet mask of 7 bits.

Some times, the subnet mask is specified with the bits available in the default subnet mask. In this case the bits available in default subnet mask is 16. Therefore, total number of bits available in the subnet mask are 16+7=23. If you are given a subnet mask of 23 bits long for a class B address, it is understood that it contains the bits from the default subnet mask as well.

Hence, 126 subnets and 510 hosts are available.

9. 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 196.233.24.15 with default subnet mask is 196.233.24.255. This is arrived by putting all 1s for the host potion of the IP address.

10. Telnet, FTP, and TFTP:

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