How DORA Works? DORA Process in Details.

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How the Host recieve the IP Address from the Server. Complete flow of DORA Process from No-IP to IP.Four stages of the DORA Process.

What is DORA?

DORA is the Process that is used by DHCP (Dynamic Host Configuration Protocol). It is used for providing the IP Address to the clients/host machine. It has four main stages and it obtains the IP Address from the centralized server.

D - Discover

O - Offer

R - Request

A - Acknowledge

Networking and Linux concepts: Dynamic Host Configuration Protocol --- DHCP

 

DHCP Discover - [BROADCAST]

  • Discover message is the first message in DORA Process which is used to find out the DHCP Server in the network. 
  • The host will send a broadcast Discover the message in the network to find a DHCP Server.

  • The packet Address is 255.255.255.255.

  • As the host doesn't have any IP Address the IP is 0.0.0.0 as of now.

  • PORTS [at Client Side - 68] / [at server side - 67].

  • The server will use the host's MAC Address to reach out to it.

  • Transaction ID: which maintains the specific DHCP session between client-server, which remains the same during [discover + offer] ] the processes.

     

Source IP: 0.0.0.0

Destination IP: 255.255.255.255

Source MAC: DHCP Client Machine MAC Address

Destination MAC: FF:FF:FF:FF:FF:FF

DHCP Offer - [UNICAST]

  • When Server Receives the Discover Request then it responds with the DHCP Offer request to the client.

  • This contains the information related to IP Address that and the lease duration that a host can use.

  • It's a unicast message.

Source IP: DHCP Server IP Address

Destination IP: 255.255.255.255

Source MAC: DHCP Server Machine MAC Address

Destination MAC: DHCP client MAC Address

DHCP Request - [BROADCAST]

  • The host receives the Offer packet then it replies back with a Request message.

  • This message tells the server that it's ready to accept the IP Address that the server Offered.

  • This IP is still 0.0.0.0 and the broadcast IP is 255.255.255.255.

Source IP: DHCP Server IP Address

Destination IP: 255.255.255.255

Source MAC: DHCP Server Machine MAC Address

Destination MAC: DHCP client MAC Address.

DHCP Acknowledge - [UNICAST]

  • The server gets the request from the host.

  • This message is a reply to the request message to the host.

  • It will send the DHCP Acknowledge request to the host along with. Which will contains the IP Address and the Subnet mask that the Server allowed for the host.

Source IP: DHCP Server IP Address

Destination IP: 255.255.255.255

Source MAC: DHCP Server Machine MAC Address

Destination MAC: DHCP client MAC Address.

 

TechMight Solutions: Dynamic Host Configuration Protocol (DHCP)

 

This is how DORA Works and the Host gets the IP Address from the Server.

Read about DHCP here - https://www.skillsire.com/read-blog/430_deployment-of-dhcp-server.html

Thanks for your time.

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