Lesson 11

Quick Recap of Lesson 10:


Key Acronym: OSPF – open shortest path first!

Classfull and Classless IP Addresses:

A  1 – 127 255.0.0.0

B 128 – 191 255.255.0.0

C 192 – 223 255.255.255.0

127 is used for pinging thus is completely excluded. There are also classes D and E but we do not need to know them just that they are there.

The default Subnet mask looks like: 255(which is network).0.0.0 (which are the nodes)

Subnet masking is for:

1. Manipulating collision domains

2. Calculating how many nodes are available on a network

Network ID

If the network ID is 121.0.0.1 then the first usable address would be 121.0.0.2

Custom IP Addresses

TCP/IP Subnets

• TCP/IP is a subnet class of leased addresses that has been divided up into smaller groups to serve all the network needs. A custom TCP/IP subnet has a custom subnet mask and ANDed to the IP Address, so that what the node sees as its local network is a subset of the whole default network address block.

• A default gateway is configured for each subnet to route traffic between the subnets.

Custom subnet masks:

• Custom Subnet masks on a Class C Network

Last octet of New Mask in Binary – New Mask Decimal - # of added networks – Nodes per network

10000000 255.255.255.128 2 126

11000000 255.255.255.192 4 62

11100000 255.255.255.224 8 30

11110000 255.255.255.240 16 14

11111000 255.255.255.248 32 6

11111100 255.255.255.252 64 2

To determine available host addresses:

The number of host address on a custom subnet is a function of the total number of address bits available for host addressing. The formula is 2 to the power or x – 2 where x is the number of host bits!



Classless Inter Domain Routing (CIDR)

• CIDR is a subnetting method that treats a VLSM as a 32 bit binary word. The mask bits can move in one bit increments to provide the exact number of nodes and networks required. CIDR notation combimes the network address with a single number to represent the number of one bits in the mask. With CIDR, multiple class based networks can be represented as a single block.

The TCP/IP Protocol Suite:

The TCP/IP Network model is a 4 layer network model which loosely follows the OSI model, the application layer maps the application, presentation and session layers in the OSI model.

3 things to remember to configure on a PC for TCP/IP addressing:

1. IP Address\

2. Subnet Mask

3. Default Gateway

Classless IP’s

How to determine your network ID?

How to determine your network mask?

EASY – RUN, CMD, ipconfig all