ARP - CCNA

ARP ( ADDRESS RESOLUTION PROTOCOL )

* it is used to find the unknown MAC address from known IP address.

* if there is no ARP, it will send a message " ENCAPSULATION FAILED ".

for example,

when a client ( user ) is connected to internet, he tries to access some websites over the internet.

during this,

* http generates a request and cover the requirement.

* in this layer, we dont know the destination IP.

DNS:

* it maintains the records of all websites.

* if we access any website, the client sends a request and after verifying it we get the request back.

PORT NUMBERS:

* these are used to identify the services.

these are of two types:

1. reserved port number ( 0 - 1023 )

2. unreserved port number ( 1024 - 65535 )

* reserved are used for identifying server side application.

* for identifying client side application, unreserved ports are used.

there are 8 process in the ARP:

1. ARP request ( fromk client to DNS )

2. ARP reply ( DNS to client )

3. DNS: name query request

4. DNS: name query response

5. ARP request ( from client to HTTP )

6. ARP reply ( from HTTP to client )

7. HTTP request

8. HTTP response