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You can use Network Registrar's client or client-class facility to provide differentiated services to users accessing a common network. You can group your user community based on administrative criteria, and then ensure that each group of users receives the appropriate class of service when they access the network.
Although Network Registrar's client-class facility can be used to control any configuration parameter, the most common uses are for:
When a client requests an IP address from its DHCP server, the server performs three tasks:
If you have multiple scopes on one subnet, and/or multiple scopes on several LAN segments (multinetting), the DHCP server may choose among these scopes, in a round-robin fashion. After the server has selected a scope, it then chooses an available IP address from that scope.
The Dynamic Host Configuration Protocol provides a framework for passing configuration information to hosts on a TCP/IP network. These configuration parameters are called DHCP options.
After the DHCP server has selected an IP address for the requesting host, it needs to supply the appropriate options. Network Registrar uses policies to group options. There are two types of policies: scope-specific and system default.
For each DHCP option the client requests, the DHCP server searches for the value of that option. If the scope-specific policy contains the option, it returns the value to the host and stops searching. If the scope-specific policy does not contain the option, the DHCP server looks in the system default policy. If the system default policy contains a value for that option, it returns the value and stops searching. If neither policy contains the option, the DHCP server returns no value to the client and logs an error. The DHCP server repeats this process for each of the requested options.
For example, if a host requests options A, B, and C, and the scope-specific policy contains a value for option A and the system default contains a value for option A and B, the host gets the value for option A from the scope policy, the value for option B from the system policy, and an error because there is no value for option C.
If you have enabled dynamic DNS update, Network Registrar enters the client's name and address in the DNS host table. The client's name can be one of the following:
You can accept the default client name, or configure another.
You can use the client-class facility to control the IP address a client receives, the type of DHCP options, the policy, or the FQDN (fully qualified domain name). You can configure any of these features independently or in conjunction with each other.
To use the client-class facility for IP address selection, you first need to create scope selection tags. These are text strings that you can use to distinguish types of service. For example, if you want to divide your user community into users who could access the Internet (and thus receive valid IP addresses) and users who are restricted to the in-house network (and thus receive private IP addresses, such as net10 addresses), you could create the scope selection tags internal and external.
After you create scope selection tags, you need to associate them with the corresponding scopes. To continue the above example, you would associate the internal scope selection tag with scopes that contain private addresses, and the external scope selection tag with scopes that contain valid IP addresses.
You then could assign each client to either include or exclude the appropriate selection tags or you could create two classes of users to group your user community into categories. For example, you could create a client-class called internal-users and include the scope selection tag internal and exclude the tag external, and the client-class external-users and include the scope selection tag external and exclude the tag internal.
When you have enabled the client-class facility for your Network Registrar DHCP server, the request processing performs the same three tasks of assigning IP addresses, options, and domain names---but with a difference.
To choose an address for the client, the DHCP server determines the client's subnet just as in regular DHCP processing. The DHCP server then checks to see if there is a client entry for the user in its database:
The scopes must have addresses on the client's subnet, and can include LAN segments. The scopes must have all the selection tags in the inclusion list, and have none of the selection tags in the exclusion list. The DHCP server assigns an available IP address from an appropriate scope, and uses a round-robin approach if there are several appropriate scopes.
The DHCP server checks each of these policies and uses the first value it finds. If the DHCP server cannot find the value for the requested option in any of these policies, it returns an error.
The DHCP server repeats this process for each client-requested option.
If you have enabled dynamic DNS updates, Network Registrar updates the DNS server with the client's host name and IP address. When using the client or client-class facility, you can specify one of the following:
You set the host name either in the Network Registrar GUI, DHCP>Client-classes>Add>Host Name or through the nrcmd client set hostname. For more information about the different types of host names that you can specify, see the Network Registrar User's Guide.
Posted: Thu Jul 13 11:05:19 PDT 2000
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