Example: Multiple TCP/IP subnets

You can learn how to set up the iSeries™ server as a DHCP server with two LANs connected by a DHCP-enabled router.

This example is similar to the previous example, Simple DHCP subnet, except that there is now an additional TCP/IP subnet. Suppose that the office and data entry clients are on different floors of a office building and separated with a router. If the network administrator wants all of the clients to receive their IP information through DHCP, this situation presents some unique differences from a simple DHCP subnet. The following figure shows an example network layout for an iSeries DHCP server connected to two LANs using a router between the networks. The figure intentionally has a limited number of clients as not to become cluttered. A real world situation has considerably more clients on each subnet.

Figure 1. Multiple LANs connected through a router

The router that connects the two networks must be enabled to pass DHCP DISCOVER packets. If it is not, the data entry clients will not be able to receive their IP information and access the network. Also, the DHCP policy needs two subnet definitions--one for the data entry and office subnets. At a minimum, the differences between the subnets are their IP subnets and router addresses. The data entry subnet needs to receive a router address of 10.1.2.2 to communicate with the office subnet.

Planning the DHCP setup for multiple LANs

Table 1. Global configuration options (applies to all clients served by the DHCP server)
Object		Value
Configuration options	option 1: Subnet mask	255.255.255.0
	option 6: Domain name server	10.1.1.1
	option 15: Domain name	mycompany.com
Subnet addresses not assigned by server		10.1.1.1 (Domain name server)
Is the server performing DNS updates?		No
Is the server supporting BOOTP clients?		No

Table 2. Subnet for Office clients
Object		Value
Subnet name		Office
Addresses to manage		10.1.1.3 - 10.1.1.150
Lease time		24 hours (default)
Configuration options	option 3: Router	10.1.1.2
Configuration options	inherited options	Options from Global configuration
Subnet addresses not assigned by server		10.1.1.2 (Router)

Table 3. Subnet for Data Entry clients
Object		Value
Subnet name		DataEntry
Addresses to manage		10.1.2.3 - 10.1.2.150
Lease time		24 hours (default)
Configuration options	option 3: Router	10.1.2.2
Configuration options	Inherited options	Options from Global configuration
Subnet addresses not assigned by server		10.1.2.2 (Router)