Example: PPP and DHCP on a single System i

 

This example explains how to set up a System i™ model as a Dynamic Host Configuration Protocol (DHCP) server for a LAN and a remote dial-in client.

Remote clients, such as dial-in clients, often require access to a company's network. Dial-in clients can gain access to a System i model with Point-to-Point Protocol (PPP) . To access the network, the dial-in client needs IP information just like any directly attached network client. A System i DHCP server can distribute IP address information to a PPP dial-in client just like any other directly attached client. The following figure shows a remote client that must dial into the company's network to do some work.

Figure 1. PPP and DHCP on a single System i model

For the remote employee to successfully become part of the company's network, the System i model must use a combination of Remote Access Services and DHCP. The Remote Access Services function creates the dial-in capability for the System i model. If set up properly, after the client establishes the dial-in connection, the PPP server tells the DHCP server to distribute TCP/IP information to the remote client.

In this example, a single DHCP subnet policy covers both the on-site network clients and the dial-in clients.

If you want your PPP profile to defer to the DHCP for IP distribution, do so in the PPP profile. In the TCP/IP settings of the receiver connection profile, set the remote IP address assignment method from Fixed to DHCP. To allow the dial-in clients to communicate with other network clients, like the LAN printer, also allow IP forwarding in the TCP/IP settings of the profile and the TCP/IP configuration (stack) properties. If you only set IP forwarding on in the PPP profile, the System i model will not pass the IP packets. You must set IP forwarding on in both the profile and the stack.

Also, the Local Interface IP address in the PPP profile must be an IP address that falls within the subnet definition in the DHCP server. In this example, the PPP profile Local Interface IP address should be 10.1.1.1. This address should also be excluded from the DHCP server's address pool so that it is not assigned to a DHCP client.

 

Planning the DHCP setup for on-site and PPP clients

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
Is the system performing DNS updates?		No
Is the system supporting BOOTP clients?		No

Table 2. Subnet for both on-site and dial-in clients

Object		Value
Subnet Name		MainNetwork
Addresses to manage		10.1.1.3 - 10.1.1.150
Lease time		24 hours (default)
Configuration options	Inherited options	Options from Global configuration
Subnet addresses not assigned by server		10.1.1.1 (Local interface address specified in the TCP/IP Settings of the Receiver Connection Profile properties in iSeries™ Navigator)

 

Other setup

• Set the Remote IP address method to DHCP in the PPP receiver connection profile.

  1. Enable DHCP WAN client connection with a DHCP server or relay connection using the Services menu item for Remote Access Services in iSeries Navigator.

  2. Select to Use DHCP for the IP address assignment method under the TCP/IP Settings Properties of the Receiver Connection Profile in iSeries Navigator.

• Allow remote system to access other networks (IP forwarding) under the TCP/IP Settings Properties of the Receiver Connection Profile in iSeries Navigator.

• Enable IP datagram forwarding under the Settings Properties of the TCP/IP Configuration in iSeries Navigator.

 

Parent topic:

Examples: DHCP

Related reference
Example: DHCP and PPP profile on different System i models