IP

Question 1

What is the length of the ip header ?

Answer 1

20 bytes , 5 layers , each layer is 4 bytes == 32 bits

Question 2

What is the purpose of icmp ?

Answer 2

Informational messages

Question 3

What are the ports required for icmp or work ?

Answer 3

No ports or listeners should be configured

Question 4

Mention 8 parts of the ip packet

Answer 4

1. Ttl
2. Fragment offset
3. Source IP
4. destination IP
5. Payload
6. Options
7. Protocol
8. Version

Question 5

If host 1 wants to talk to host 5 , and only have it’s ip how can it get the mac address of 5 ?

Answer 5

It will use ARP and send ARP broadcast to all host to get the MAC of host 5

Question 6

What is the flow of request when i have the ip of another host and want to talk to it ?

Answer 6

1. Check if the ip is in my subnet (AND ops between subnet mask and ip )
2. Check if the mac address is within my ARP table
3. Send ARP Broadcast

Question 7

What if the ip is not within my subnet mask , where the routing will go ?

Answer 7

I will go to my gateway (router) and it will handle the routing

Question 8

How is public ip get bought ?

Answer 8

RIR : regional internet registries
RIPE NCC : resaux IP Europe network center coordination

Question 9

Why do we need a default GW ?

Answer 9

To route requests to hosts outside our subnet

Question 10

How to find if two ips are in the same subnet or not ?

Answer 10

First req : do AND operation between first ip and its subnet mask

Second req : do AND operation between second ip and its subnet mask

Compare the output of both operations , if different then they are in different subnets