Scenario: DHCP and PPP profile on different IBM i models
This scenario explains how to set up two IBM® i models as the network Dynamic Host Configuration Protocol (DHCP) server and the BOOTP/DHCP relay agent for two LANs and remote dial-in clients.
The scenario about PPP and DHCP on a single IBM i model shows how to use PPP and DHCP on a single system to permit dial-in clients access to a network. If you are concerned with the physical layout of your network or with security, it might be better to have the PPP and DHCP servers separated or to have a dedicated PPP server without DHCP services. The following figure represents a network that has dial-in clients with the PPP and DHCP policies on different servers.
The remote data entry clients dial into the IBM i PPP server. The PPP profile on that server must have a remote IP address method of DHCP, such as the one used in the scenario of PPP and DHCP on a single IBM i model. The PPP profile and the TCP/IP settings on the PPP profile must have IP forwarding. Furthermore, because this server is acting as a DHCP relay agent, the BOOTP/DHCP relay agent must be on. This allows the IBM i Remote Access server to pass on DHCPDISCOVER packets to the DHCP server. The DHCP server then responds and distributes TCP/IP information to the dial-in clients through the PPP server.
The DHCP server is responsible for distributing IP addresses to both the 10.1.1.0 and 10.1.2.0 networks. In the data entry network, the DHCP server gives out IP addresses ranging from 10.1.2.10 to 10.1.2.40 to either dial-in or directly attached network clients. The data entry clients also need a router address (option 3) of 10.1.2.1 to communicate with the work network, and the IBM i DHCP server must also have IP forwarding enabled.
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 scenario, the PPP profile Local Interface address must be 10.1.2.2. This address must also be excluded from the DHCP server's address pool so that it is not assigned to a DHCP client. The local interface IP address must be an address to which the DHCP server can send reply packets to.
Planning the DHCP setup for DHCP with a DHCP relay agent
| 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 | |
| Object | Value | |
|---|---|---|
| Subnet name | WorkNetwork | |
| 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 | none | |
| Object | Value | |
|---|---|---|
| Subnet Name | DataEntry | |
| Addresses to manage | 10.1.2.10 - 10.1.2.40 | |
| Lease time | 24 hours (default) | |
| Configuration options | Option 3: Router | 10.1.2.1 |
| Inherited options | Options from Global configuration | |
| Subnet addresses not assigned by server | 10.1.2.1 (Router)
10.1.2.15 (Remote Data Entry client's local interface IP address) 10.1.2.14 (Remote Data Entry client's local interface IP address) |
|
Other setup on a IBM i platform running PPP
- Set up the BOOTP/DHCP relay agent TCP/IP server
Object Value Interface address 10.1.2.2 Relay packets to Server IP address 10.1.2.1 - Set the Remote IP address method to DHCP in the PPP receiver connection
profile
- Enable DHCP WAN client connection with a DHCP server or relay connection using the Services task for Remote Access Services in IBM Navigator for i
- Select to Use DHCP for the IP address assignment method under the TCP/IP IPv4 Settings Properties of the Receiver Connection Profile in IBM Navigator for i
- Allow remote system to access other networks (IP forwarding) under the TCP/IP IPv4 Settings Properties of the Receiver Connection Profile in IBM Navigator for i (to allow the remote clients to communicate with the data entry network)
- Enable IP datagram forwarding under the TCP/IP Attributes in IBM Navigator for i (to allow the remote clients to communicate with the data entry network)