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Dated: Jul. 17, 2012

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Overview of DHCP Classes

DHCP classes are the categories for which when DHCP client computers are configured, they receive a different predefined set of DNS servers’ addresses, addresses of the default gateways, etc. There are three types of classes that DHCP servers allow administrators to work with. They are:

  • Default Class
  • User Class
  • Vendor Class

User and Vendor classes must be created manually by the DHCP administrators whereas Default classes are created automatically as soon as the role of the DHCP server is installed on the network operating systems. By default all DHCP clients are configured as the default class clients and receive dynamic addresses as per the default DHCP class scopes.

Understanding DHCP ClassesIn small-scale organizations and home environments, DHCP servers are installed normally and no class oriented configurations are done. The reason behind this is that by default all DHCP client computers belong to default DHCP class and as soon as DHCP scopes are configured and the DHCP servers become ready to assign dynamic addresses to the client computers, the DHCP clients start receiving the IP addresses without any additional administrative overheads. However, in order to allow DHCP servers to assign different sets of DNS and default gateway addresses to the DHCP client computers, DHCP User or Vendor classes must be created and the DHCP clients must be configured to obtain those set of addresses from their respective DHCP classes. To do so, the default class of the DHCP clients must be changed and the computers must be set to User or Vendor classes.

Details About the 3 DHCP Classes Are:

Default Class: This DHCP class is by default configured as soon as the DHCP server role is installed on the network operating systems. After the successful installation of DHCP server roles, administrators must create DHCP scopes where they must specify a range of IP addresses along with the addresses of the DNS servers and the default gateways. Since all DHCP client computers by default belong to default DHCP class, they receive the set of addresses from the default class only.

User Class: This DHCP class must be created manually by the administrators. User class is created in the environments where a computer or a group of computers is to be redirected to the different network or a specific computer by assigning addresses of different DNS server and/or the default gateway. An example can be of accounts department in an organization, computers of which need to access highly sensitive information from file servers that are kept isolated from the rest of the organization’s network. Since such file servers may have different IP addresses that may belong to different network addresses or different address classes altogether, creating User classes and specifying addresses of DNS servers and default gateways that redirect the queries to the sensitive and isolated file servers make the network setup quite efficient and highly secured.

Vendor Class: This DHCP class works in the same manner as User class does, i.e. it also provides a different set of address of DNS servers and default gateways to the DHCP client computers. However, Vendor classes are created when a network setup has multi-platform environment and the administrators want the DHCP client computers running non-Microsoft operating systems to obtain a different set of DNS and default gateway addresses. For example, in an organization some computers have Microsoft Windows 7 installed on them and receive as their DNS and default gateways. On the other hand, other computers have Linux OS installed on them. A Vendor class for Linux can be created so that all Linux clients can be assigned with different DNS and default gateway addresses, e.g.

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