DHCP

 DHCP Questions:

DHCP server within the subnet

                DHCP Discover(Broad cast)

client  -----------------------------> server

              DHCP offer(unicast/ Broadcast)

client  <----------------------------- server

        DHCP Request(Broad cast)

client  -----------------------------> server

     DHCP ACK(Broad cast/ Unicast)

client  <----------------------------- server

Got the IP.

2) DHCP server outof the subnet, DHCP proxy and relay:

When the server is out of subnet, The router acts as relay agent with its b'wn the client and server.

client sends broadcast packet to router, The router configured as relay agent forwards the packet convert ing the broadcast packet to unicast packet.

The relay agent includes its own IP address in the Gateway IP address field to let know the server in which subnet client  is located to assign an IP address.

The DHCP server sends back/forwards the offer packet to the relay agent with the offered address from the subnet based on gateway address field.

The relay agent receives the server's unicast DHCPOFFER and forwards it back to the original client via broadcast

The client then sends a DHCPREQUEST message as Braodcast msg through the relay agent. 

The server responds with a DHCPACK, confirming the assignment of the IP address.

The relay agent forwards these messages between the client and server as necessary

DHCP client renews lease time when expires

DHCP options.

DHCP port numbers.

68