DHCP Dora process is handling by a SERVER called DHCP SERVER that dynamically distributes network configuration parameters, such as IP Addresses for interface or services. It is a standardized network protocol used on INTERNET PROTOCOL in the network. About DHCP SERVER, it can be a ROUTER that SERVER enables computers to request IP Address and networking parameters automatically and no need manual configuration.
What is DHCP?
In any network, if a host wants to communicate with another host, then it must have a unique IP address for it. Whether it is a local area network or a wide area network. The work of DHCP is to assign an IP address to the hosts. DHCP is a client/server protocol. DHCP port number is 67 and 68. DHCP client work on port number 67 and DHCP server work on port number 68.
DHCP work as a client – Server Model, here SERVER handling the clients. DHCP employs a connectionless service model using UDP (User Datagram Protocol). Two UDP port used in the DHCP process, 67 UDP port is the destination port of a server and 68 UDP port used by the client.
DHCP SERVER – DHCP SERVER working in the same networking means it provides IPs in the same network. DHCP SERVER automatically provides the IPs to clients. DHCP server manages a pool of IPs & information about clients such parameter DEFAULT GATEWAY, DOMAIN NAME, SERVER NAME, & TIME SERVER.
How does the DHCP Dora process work?
DHCP operation divides into 4 phases.
- Server Discovery
- IP Lease Offer
- IP Lease Request
- IP lease Acknowledgement
This DHCP operation called DORA Process.
Note * For example I used unicast IP Address.
First I am telling you about DORA process in DHCP
Discovery ( DHCP discover ):
By this message interaction start between server and client. Discovery sent by a client that is connected to a local subnet. While send discovery destination address is broadcast 255.255.255.255 and source address is 0.0.0.0.
OFFER ( DHCP offer ):
Offer is a response to the Discovery message by the DHCP server to the DHCP clients. It contains a network configuration setting for the client like an IP address offered to client 10.1.1.1.
REQUEST ( DHCP request ):
Response to Offer is indicating that the client has accepted the network configuration. It means to accept the offer by the DHCP server with IP 10.1.1.1. this message sent by the client with destination address 255.255.255.255 and the source address is 10.1.1.1.
ACKNOWLEDGE ( DHCP ack ):
After the request message or accept the IP by DHCP SERVER, the server sent an ACK to the client. This message clear to the client that now you can start using the network.
This four-phase of DORA process and describe how IP assign to a Client by DHCP server. By default Receiver or client receive IP from DHCP SERVER for 24 Hour. By using time connectivity is fine or message always going unicast.
After 50% time (12 hours): Connectivity is ok then IP is renewing 24 hours, if no then time goes on.
After 75% time (18 hours): Connectivity is ok then IP is renewing for 24 hours if no then the left time going on continues.
After 100% time (24 Hours): Connectivity is ok then IP is renewing for 24 hours if connectivity no then IP got by APIPA 169.254.255.0.
Automatic Private IP Address 169.254.255.0. APIPA work in some situations: When DHCP SERVER not available. When connectivity is not there with network If DHCP SERVER has any problem.
Advantage of APIPA
- It works the same as DHCP SERVER
- It stops unwanted Broadcast.
- How to configure DHCP and pool
Router(config)#ip DHCP pool vlan10
Router(DHCP-config)#network 192.168.10.0 /24
Router# show IP DHCP pool (By this command check the pool status)
The above blog is all about DHCP. From this, you can clarify what is DHCP and how it functions in networking. DHCP is mostly asking in an interview (Domestic and MNC companies).
May it help you, after you read this blog I am sure you can describe the DHCP and How to operate DHCP or DHCP server and what is the relation of SERVER and CLIENT and DORA process etc.