DHCP

• Stands for dynamic host configuration protocol.
• DHCP is a network protocol that enables a server to automatically assign an IP address to a computer from a defined range of numbers configured for a given network.
• DHCP allows hosts to obtain necessary TCP/IP configuration information from a DHCP server.
• Without DHCP, IP addresses must be configured manually for new computers or computers that are moved from one subnet to another, and manually reclaimed for computers that are removed from the network.
• Because the IP addresses are dynamic rather than static, addresses no longer in use are automatically returned to the pool for reallocation.

Allocation of IP address

Depending on implementation, the DHCP server may have three methods of allocating IP addresses:
1. Dynamic allocation

• A network administrator reserves a range of IP addresses for DHCP, and each DHCP client on the LAN is configured to request an IP address from the DHCP server during network initialization.
• The request and grant process uses a lease concept with a controllable time period, allowing the DHCP server to reclaim IP addresses that are not renewed.

2. Automatic allocation

• The DHCP server permanently assigns an IP address to a requesting client from the range defined by the administrator.
• This is like dynamic allocation, but the DHCP server keeps a table of past IP address assignments, so that it can preferentially assign to a client the same IP address that the client previously had.

3. Manual allocation

• The address is set based on the user's request.
• The address could be out of the DHCP allocated pool.

Working process

1. DHCP server receive a request from host.
2. Server selects IP address information from a database.
3. servers offers the addresses to requesting host.
4. If the host accept the offer, the server leases the IP address for a specific period of time.

Advantages

• IP address management.
• It have large network support.
• To implement DHCP do not require additional cost.
• DHCP servers only allocate IP address to client when they request them.

Disadvantages

• Your machine name does not change when you get a new IP address.
• DHCP server is unavailable client unable to access enterprises network.
• DNS cannot be used for DHCP configured hosts.