Chapter 1 - Internetworking- 01

INTERNETWOKING BASICS

 

Why is it so important to study CCNA internetwoking?

 

Networks and netwoking have grown so fastly during last over few decades. In order to keep up with huge increases in basic mission, sharing data and printers as well as very advanced demands such as videoconferencing, They've had to evlove at light speed. However, there is a challenge because sometimes many relevant networks together and all users want to share the network's wealth. Moreover, those who needs to share network resources aren't located in the same area.

Figure 1.1 the basic network

  Figure 1.1, you get a picture of a basic LAN network that connected together using a hub. This network is actually one collision domain and one broadcast domain. About Figure 1.1, How would the A communicates with the B ? Actually, they're both on the same LAN connected with a multiport repeater(a hub). Then, if A want to send out some messages to B, how would you know the exactly process? If you choose the answer for this question like "192.168.0.3, hello world", Your answer is wrong. Because, A is actually going to use B's MAC address(hardware address). Then, how does A get B's MAC address since A knows only B's name and doesn't even have its IP address yet? A is going to start with name resolution(hostname to IP address resolution). This is what we called Domain Name Service(DNS). And of note, these two are on the same LAN, A can broadcast to B to send out message, and it doesn't need DNS information. 

Just broadcast to resolve the name B(the destination 192.168.0.255 is a broadcast address)

And talking about more information such as Ethernet2, Src:192.168.0.2(00:14:22:be:18:3b), Dst:Broadcast (ff:ff:ff:ff:ff:ff).

What this output shows that A knows its own IP and MAC address but not B's IP and MAC, so A sends a broadcast address all fs for the MAC address (a Data link layer broadcast) and an IP LAN broadcast of a 192.168.0.255 again. Before the name is resolved, the first thing A has to do is broadcast on the LAN to get B's MAC address so A can communicate to B and resolve B's name to an IP addres.

ARP is Address Resolution Protocol, and it used for binding IP address to MAC address in Network

Next, B will response like that

Now A has both B's IP and MAC address. These are both listed as the source address at this point. By the way, there are still many things have to do. You will have to break up one large network into a bunch of smaller ones because user response will have dwindled to a slow crawl as the network grew and grew. And with all that growth, your LAN's traffic congestion has reached epic proportions. The answer to this is breaking up a really big network into a number of smaller ones what we called "Network Segmentation". You do this by using devices like routers, switches, bridges. Next time, i am going to talk about handling this issues.