What Is Dynamic Host Configuration Protocol

The Dynamic Host Configuration Protocol(DHCP) is a network management protocol used on Internet Protocol networks for automatically assigning IP addresses and other communication parameters to devices connected to the network using a client–server architecture.

Dynamic Host Configuration Protocol (DHCP) is a network management protocol used to automate the process of configuring devices on IP networks, thus allowing them to use network services such as DNS, NTP, and any communication protocol based on UDP or TCP. A DHCP server dynamically assigns an IP address and other network configuration parameters to each device on a network so they can communicate with other IP networks. DHCP is an enhancement of an older protocol called BOOTP. DHCP is an important part of the DDI solution (DNS-DHCP-IPAM).

Implementation of DHCP Service

The original and most comprehensive implementation of the DHCP service is offered by the Internet Systems Consortium (ISC). Supporting both IPv4 and IPv6, ISC DHCP offers a complete open source solution for implementing DHCP servers, relay agents, and clients. Other DHCP Server products include the Microsoft DHCP server.

The DHCP service can be enhanced by DHCP failover to bring high availability and load balancing of traffic. The ISC DHCP Failover relies on having a pair of collaborating servers – a primary (master) server and a secondary (backup) server. A TCP-based communication channel, called a failover channel, then has to be set up between the two servers.

What is the main function of DHCP?

A DHCP Server is a network server that automatically provides and assigns IP addresses, default gateways and other network parameters to client devices. It relies on the standard protocol known as Dynamic Host Configuration Protocol or DHCP to respond to broadcast queries by clients.

WHAT IS DHCP CLIENT?

A DHCP client is an Internet host using DHCP to obtain configuration parameters such as an IP address. … A DHCP server offers configuration parameters (such as an IP address, a MAC address, a domain name, and a lease for the IP address) to the client in a DHCPOFFER unicast message.

What Is a DHCP Client List?
When DHCP is enabled, multiple computers and other devices, such as smartphones, tablets, and wireless printers will be assigned IP addresses. Sometimes, you may need to know the IP address of a particular device or you may need to track who is connecting to your network. In either of these cases, you can access the DHCP Client List for this data.

This client list is simply a list of the devices and IP numbers that are assigned through the server or router. This list contains all devices that are connected to the network through wired or wireless connections. If DHCP is not enabled, you will not have access to this list. Devices that are not connected through the network also will not appear on the list.

Accessing Your DHCP Client List
Though instructions may vary slightly by router manufacturer, generally the instructions are the same for accessing your DHCP Client List. To begin, enter your IP address into your browser’s search bar. This will take you to your router settings, where you’ll be able to enable or disable DHCP, change other settings, and view your DHCP Client List.

The next steps may vary slightly depending on the type of router you have, but most routers will have a Network Setup section. Access this section to make sure DHCP has been enabled. You may be able to access your list through this menu, although you may have to navigate to another section, such as Local Networks. Remember, if you get lost or confused, you can check out your router’s user manual or visit the manufacturer’s website.

You should see an option within the router settings called, “DHCP Client Table.” Click this option to view the table, also known as your Client List. Usually, there are several settings for this table. These include a refresh mode to provide you with an updated list, a delete option, and a sort mode for sorting through your list. Again, these options vary by manufacturer, so your options may be slightly different.

Once you’ve reviewed your list, make sure to save any changes and close your router settings.

What is DHCP client identifier?

What is meant by client identifier?

client-id—A name or number that uniquely identifies the client on the network. The client identifier can be an ASCII string or hexadecimal digits

WHAT IS DHCP SERVER?

A DHCP Server is a network server that automatically provides and assigns IP addresses, default gateways and other network parameters to client devices. It relies on the standard protocol known as Dynamic Host Configuration Protocol or DHCP to respond to broadcast queries by clients.

A DHCP server automatically sends the required network parameters for clients to properly communicate on the network. Without it, the network administrator has to manually set up every client that joins the network, which can be cumbersome, especially in large networks. DHCP servers usually assign each client with a unique dynamic IP address, which changes when the client’s lease for that IP address has expired.

When to use a router/switch as your DHCP Server
There are many enterprise companies who are still using DHCP for IPv4 on their routers/switches.  This is typically done by the network administrator who needs to get a DHCP capability up and running quickly but does not have access to a DHCP server. Most routers/switches have the ability to provide the following DHCP server support:

• a DHCP client and obtain an interface IPv4 address from an upstream DHCP service
• a DHCP relay and forward UDP DHCP messages from clients on a LAN to and from a DHCP server
• a DHCP server whereby the router/switch services DHCP requests directly. However, there are limitations to using a router/switch as a DHCP server
• Running a DHCP server on a router/switch consumes resources on the network device.  These DHCP packets are handled in software (not hardware accelerated forwarding).  The resources required make this practice not suitable for a network with a large number (> 150) of DHCP clients.
• Does not support dynamic DNS.  The router/switch DHCP server cannot create an entry into DNS on behalf of the client based on the IPv4 address that was leased to the client.
• No ability to e asily manage the scope and see the current DHCP bindings and leases across multiple routers.  Administrator must log into the switch/router individually to get information about DHCP bindings.
• No high availability or redundancy of the DHCP bindings.  This could cause problems if the current DHCP server and default gateway fails.
• It is more difficult to configure DHCP options on router/switch platform.
• The DHCP service running on a router/switch is not integrated with IP address management (IPAM) for address tracking and scope utilization or security forensics.

The Benefits of a dedicated DHCP Server
A better approach than trying to use DHCP on your router/switch is to use a centralized DHCP server. This is particularly true for network environments that require support of both DHCP for IPv4 and DHCP for IPv6 at the same time.  Virtually all DHCP server vendors support both protocols so you can use the same management interface for IPv4 and IPv6.  There are several benefits that make it advantageous for an enterprise to use DHCPv6.

• Having a DHCPv6 server that is integrated into your IP Address Management (IPAM) system for IPv6 gives visibility to the IPv6-enabled client nodes.
• You also would want this same functionality for IPv4.  As IPv4 address space becomes increasingly constrained, you will want to keep track of your DHCP scopes and determine if your lease time is adequate with the plethora of BYOD systems joining your networked environment.
• DHCP servers provide logging and management interfaces that aid administrators manage their IP address scopes.  Your organization will want an accounting of what is on your network regardless of IP version being used.
• DHCP servers can provide redundancy and high availability.  If one DHCP server were to fail, the clients will preserve their current IP addresses and not cause an interruption for the end-nodes.
• Organizations will prefer a DHCPv6 server that has been tried and tested.  For example, The Infoblox DHCPv6 server has been certified as “IPv6 Ready” by the USGv6 certification laboratory.

Organizations that are beginning to implement IPv6 should migrate DHCP for IPv4 scope off the routers/switches and put them on a robust DHCP server infrastructure. This change will also mean that your organization would want to have DHCP operate the same for both protocols.  Enterprise organizations will want to take advantage of the centralized dual-protocol DHCP server to provide IPv4 and IPv6 addresses to client devices. 

Why use DHCP?

Every device on a TCP/IP-based network must have a unique unicast IP address to access the network and its resources. Without DHCP, IP addresses for new computers or computers that are moved from one subnet to another must be configured manually; IP addresses for computers that are removed from the network must be manually reclaimed.

With DHCP, this entire process is automated and managed centrally. The DHCP server maintains a pool of IP addresses and leases an address to any DHCP-enabled client when it starts up on the network. Because the IP addresses are dynamic (leased) rather than static (permanently assigned), addresses no longer in use are automatically returned to the pool for reallocation.

The network administrator establishes DHCP servers that maintain TCP/IP configuration information and provide address configuration to DHCP-enabled clients in the form of a lease offer. The DHCP server stores the configuration information in a database that includes:

• Valid TCP/IP configuration parameters for all clients on the network.
• Valid IP addresses, maintained in a pool for assignment to clients, as well as excluded addresses.
• Reserved IP addresses associated with particular DHCP clients. This allows consistent assignment of a single IP address to a single DHCP client.
• The lease duration, or the length of time for which the IP address can be used before a lease renewal is required.

A DHCP-enabled client, upon accepting a lease offer, receives:

• A valid IP address for the subnet to which it is connecting.
• Requested DHCP options, which are additional parameters that a DHCP server is configured to assign to clients. Some examples of DHCP options are Router (default gateway), DNS Servers, and DNS Domain Name.

Benefits of DHCP

DHCP provides the following benefits.

• Reliable IP address configuration. DHCP minimizes configuration errors caused by manual IP address configuration, such as typographical errors, or address conflicts caused by the assignment of an IP address to more than one computer at the same time.
• Reduced network administration. DHCP includes the following features to reduce network administration:
  • Centralized and automated TCP/IP configuration.
  • The ability to define TCP/IP configurations from a central location.
  • The ability to assign a full range of additional TCP/IP configuration values by means of DHCP options.
  • The efficient handling of IP address changes for clients that must be updated frequently, such as those for portable devices that move to different locations on a wireless network.
  • The forwarding of initial DHCP messages by using a DHCP relay agent, which eliminates the need for a DHCP server on every subnet.

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