Setting up the DNS and DHCP for IBM Spectrum Fusion appliance

As a prerequisite to IBM Spectrum Fusion HCI installation, update Dynamic Host Configuration Protocol (DHCP) and Domain Name System (DNS) with the information detailed in the planning worksheet for your system.

Before you begin

Download the installation preparation worksheet and review the network preparation section. To download the worksheets, see IBM Spectrum Fusion HCI Installation worksheets.

  • Ensure that you have the MAC addresses from your IBM Technical Seller with whom you engaged with. If you do not have your IBM Technical Seller contact information, see the planning worksheets for contact details.

    To download the worksheets, see IBM Spectrum Fusion HCI Installation worksheets.

    For DHCP configuration of bootstrap VM, you must use the MAC address of ru7VM provided in the mail from IBM Technical Seller. For example, ru7VM 00:16:3e:11:4d:dd.

  • The sample files that are used in this section are based on standard DNS/DHCP services available on Red Hat® Enterprise Linux 8.

About this task

You can access IBM Spectrum Fusion OpenShift® Container Platform cluster nodes on your network. As such, each cluster node requires an IP address that is accessible on this network. During installation, each cluster node obtains its IP address from an external DHCP server based on the MAC address of the cluster node. As a prerequisite for IBM Spectrum Fusion HCI installation, you must reserve a number of IP addresses for OpenShift:
  • One IP address for the OpenShift API server endpoint
  • One IP address for the wildcard ingress endpoint (to access your workloads)
  • One IP address for each cluster node (control, compute, AFM, and GPU nodes)
  • One IP address for the bootstrap node (it is temporary and is only required during the OpenShift Container Platform installation)
Note: For each cluster node and the bootstrap node, you must add DHCP reservations to your DHCP configuration.
A single sample DHCP reservation record for a cluster node looks similar to the following example:
host control-0.isf.mycompany.com { option host-name "control-0.isf.mycompany.com"; hardware ethernet 04:3f:72:f7:2f:76; fixed-address 10.44.100.145;

IBM provides the node's hostname (for example, control-0) and hardware Ethernet (MAC) address and you cannot change them. The fixed-address that you provide is the IP address that gets assigned to the cluster node.

A fully functional DNS environment is a requirement for IBM Spectrum Fusion HCI and OpenShift Enterprise to work correctly. Adding entries into the /etc/hosts file is not enough because that file is not copied into containers that are running on the platform. For more information about DHCP and DNS, see OpenShift documentation.

For a single rack, mapping of rack unit with OpenShift host name:
Rack unit Host name Node type
RU2 control-0 Storage
RU3 control-1 Storage
RU4 control-2 Storage
RU5 compute-0 Storage
RU6 compute-1 Storage
RU7 compute-2 Storage
RU8 compute-3 Storage
RU9 compute-4 Storage
RU10 compute-5 Storage
RU11 compute-6 Storage
RU12 compute-7 Storage
RU13 compute-8 Storage
RU14 compute-9 Storage
RU15 compute-10 Storage
RU16 compute-11 Storage
RU17 compute-12 Storage
RU23 compute-13 AFM
RU24 compute-14 AFM
RU25* compute-15 GPU
RU27* compute-16 GPU
RU29 compute-17 Storage
RU30 compute-18 Storage
RU31** compute-19 Storage
RU32** compute-20 Storage

* GPU nodes occupy two rack units.

** Nodes are mutually exclusive with the GPU nodes.

Procedure

  1. Place your DHCP servers in the same VLAN as IBM Spectrum Fusion HCI unless the DHCP relay agent is used.
  2. Verify whether the DNS server is accessible from outside the IBM Spectrum Fusion HCI by using either the ping <server-ipaddress> or the nslookup <server-ipaddress> command.
    Note: The DNS server can be anywhere but must be reachable, that is, the installation and cluster must have access to your network.
  3. After the verification is complete, set up DHCP reservation for each node. For more information about setting up the DHCP, see Setting up DHCP.
  4. Set up the DNS reservation for each node. For more information about setting up the DNS, see Setting up DNS.
    Here, ensure you use the same domain-name-servers value and option host name that you used in DHCP configuration as they are interconnected. Make sure that the fixed addresses that you configure here must be the same in DHCP as well.