DHCP Short for Dynamic Host Configuration Protocol, a protocol for assigning dynamic IP addresses to devices on a network. With dynamic addressing, a device can have a different IP address every time it connects to the network. In some systems, the device’s IP address can even change while it is still connected. DHCP also supports a mix of static and dynamic IP addresses.

Dynamic addressing simplifies network administration because the software keeps track of IP addresses rather than requiring an administrator to manage the task. This means that a new computer can be added to a network without the hassle of manually assigning it a unique IP address. Many ISPs use dynamic IP addressing for dial-up users. This protocol reduces administrators workload which allows addition of devices to the network little or zero manual intervention.

dhcp-3-300x288 DHCP.

DHCP is a way of managing network parameter assignment from a single DHCP server or may be a group of DHCP servers arranged in a fault tolerant style. Using DHCP any new machine can be added to the local network. DHCP can be used to assign addresses directly to the desktop machines or servers.

dhcp2 DHCP.

Technical Summary

DHCP uses two IANA assigned ports as BOOTP: 67/udp for the server side, and 68/udp for the client side.

DHCP works in four phases :

  1. IP Discovery ,
  2. IP Lease Offer,
  3. IP Request and
  4. IP lease acknowledgement.

After the client gets an IP address, he may start an address resolution (ARP) query for preventing IP conflicts caused due to address pool overlapping of DHCP servers.

safe_dhcp_quarantine DHCP.

Security

The basic DHCP does not have any feature of security hence is susceptible to two types of attacks.

  1. Unauthorized DHCP Servers : One cannot specify the required server. Any unauthorized server may react to the clients request and send client network configuration to the hacker.
  2. Unauthorized DHCP clients : An unauthorized client can gain access to the network configuration and IP address by camouflaging itself as a legitimate client.

RFC3118 introduced authentication information into DHCP messages to overcome these threats. Doing this enables the clients and servers to reject information from invalid or unknown sources.