HMC as a DHCP server

You can use the Hardware Management Console (HMC) as a Dynamic Host Configuration Protocol (DHCP) server.

If you want to configure the first network interface as a private network, you can select from a range of IP addresses for the DHCP server to assign to its clients. The selectable address ranges include segments from the standard nonroutable IP address ranges.

In addition to these standard ranges, a special range of IP addresses is reserved for IP addresses. This special range can be used to avoid conflicts in cases where the HMC attached open networks are using one of the nonroutable address ranges. Based on the range that is selected, the HMC network interface on the private network is automatically assigned the first IP address of that range, and the service processors are then assigned addresses from the rest of the range.

The DHCP server in the HMC uses automatic allocation, which means that each unique service processor Ethernet interface is reassigned the same IP address each time it is started. Each Ethernet interface has a unique identifier that is based on a built-in Media Access Control (MAC) address, which allows the DHCP server to reassign the same IP parameters. You can configure both eth0 and eth1 HMC ports to serve DHCP addresses.You can configure both eth0 and eth1 HMC ports to serve DHCP addresses.

Figure 1. Private network with one HMC as a DHCP server

Note: If you are using IPv6, the discovery process must be done manually. For IPv6, automatic discovery is not available.

For more information about how to configure the HMC as a DHCP server, see Configuring the HMC as a DHCP server.

Redundant HMC with two managed systems shown.

This figure shows a redundant HMC environment with two managed systems. The first HMC is connected to the first port on each FSP, and the redundant HMC is connected to the second port on each HMC. Each HMC is configured as a DHCP server, by using a different range of IP addresses. The connections are on separate private networks. As such, it is important to ensure that no FSP port is connected to more than one HMC.

Each managed system's FSP port that is connected to an HMC requires a unique IP address. To ensure that each FSP has a unique IP address, use the HMC's built-in DHCP server capability. When the FSP detects the active network link, it issues a broadcast request to locate a DHCP server. When correctly configured, the HMC responds to that request by allocating one of a selected range of addresses.

If you have multiple FSPs, you must have your own LAN switch or hub for the HMC to FSP private network. Alternately, this private segment can exist as several ports in a private virtual LAN (VLAN) on a larger managed switch. If you have multiple private VLANs, you must ensure that they are isolated and without any crossover traffic.

If you have more than one HMC, you must also connect each HMC to the logical partitions, and to each other, on the same open network.

HMC connected to a single managed server on a private network and to three logical partitions on the public network shown.

This figure shows two HMCs connected to a single managed server on the private network and to three logical partitions on the public network. You can have an extra Ethernet adapter for the HMC to have three network interfaces. You can use this third network as a management network or connect it to the CSM (Cluster Systems Manager) Management Server.