The Computer is a very complicated device we use for our every day comfort and the importance of some of its numerical aspects is sometimes neglected. For example: a different number is given to each computer when its user goes online or when it is part of a network. This number is the IP address and knowing about it is like knowing where you live…

What’s my IP and what do its numbers stand for?
IP stands for Internet Protocol and the address is formed from 4 numbers separated by periods. The IP address format is a 32 bit numeric one and each number can be from 0 to 255. The IP address consists of two parts: first one represent the network number and it is similar for more than one user (like the number of a street) and second represents the host name which is different for each user (like the house number). To increase the number of available IP addresses within big networks with a lot of users or small networks with few hosts, the address is divided into 4 classes (A, B, C, and D)

Having an IP address it’s like having a last name in a network. To identify a computer in a network (LAN-local area network, WAN-wide area network or on the Internet) it has to have an IP address. This number is similar to a phone number or to a zip code. It is unique and without it the device or computer can not be used in a network area. Within an isolated network the computers can be assigned different random IP addresses, but if a private network needs to be connected to the Internet the IP has to be registered so that its uniqueness is verified.
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To pass the BSCI exam and move one step closer to CCNP certification success, you’ve got to know how and when to use debug commands to troubleshoot and verify network operations. While you should never practice debug commands on a production network, it’s important to get some hands-on experience with them and not rely on “router simulators” and books to learn about them.

When it comes to RIP, “debug ip rip” is the primary debug to use. This debug will show you the contents of the routing update packets, and is vital in diagnosing RIP version mismatches and routing update authentication issues.

You know how to use the variance command to configure unequal-cost load-sharing with IGRP, but IGRP has no topology table that will give you the feasible successor metrics you need. With IGRP, you need to use the “debug ip igrp transactions” command to get these vital metrics.
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1. Network interface(Data link) layer
2. Network layer
3. Transport layer
4. Application layer

Network interface layer
The lowest layer of the TCP/IP model. Its task is to provide access to the transmission physical medium and it differs according to the implementation of the medium.

Network layer
The network layer provides network addressing, routing and datagram transmission. Used protocols that will be of interest further regarding DHCP are IP and ARP.

IP protocol
It is the basic protocol of the network layer and in general the internet as a whole. It sends datagrams, which are independent units that contain information about the destination, source and the sequence number of the datagram. The sequence number is used for message reconstruction, since the delivery order of the datagrams might not be the same as their order in the message and delivery reliability isn’t guaranteed at all.
IP protocol versions:
” IP v4 – 32 bit addresses. Provides approximately 4 billion unique addresses which aren’t sufficient at present times.
” IP v6 – 128 bit addresses. The transition to v6 will bring (is bringing) higher security, QoS, packet segmentation and many more IP addresses. (the transition from IP v4 to IP v6 must be supported by the system provider)
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