Network planning

As you plan for installing systems in your data center, review information about the network resources and your configuration options.

This topic is mainly intended for your network administrator.

Important: Complete the planning worksheets to provide IBM Service Support Representative (SSR) with the IBM Spectrum Fusion HCI network setup plan.

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

Configure DHCP and DNS

For the steps to configure DHCP and DNS, see Setting up the DNS and DHCP for IBM Spectrum Fusion appliance.

Ensure that you complete your Domain Name System (DNS) and Dynamic Host Configuration Protocol (DHCP) setup. For more information about setting your DHCP and DNS, see Setting up the DNS and DHCP for IBM Spectrum Fusion appliance.

Ensuring that your DHCP server can provide infinite leases

Your DHCP server must provide a DHCP expiration time of 4294967295 seconds to properly set an infinite lease as specified by rfc2131. If a lesser value is returned for the DHCP infinite lease time, the node reports an error and a permanent IP is not set for the node. In RHEL 8, dhcpd does not provide infinite leases. If you want to use the provisioner node to serve dynamic IP addresses with infinite lease times, use dnsmasq rather than dhcpd.

Configure NTP

Ensure that the network administrator has configured an NTP server that is connected to your network.

Network cable requirements

For network cable requirements and multi-rack cable and transceiver requirements, see Network cable and transceiver options.

Resources

Note: The Link name and VLAN ID must not have special characters. Interface names can be a maximum of 15 characters. You cannot use a number for the first character and you cannot include a dash [-] in the name. In addition, you cannot use any name that matches with the regular expression .{0,13}\-v.*.

VLANs

A virtual LAN (VLAN) is an isolated broadcast domain that is created within a switch. Each VLAN created within a switch is isolated from other VLANs. The network traffic can pass from one VLAN to another by adding a routing device. The routing functions must be provided at the data center core network.

Internal Management VLAN: It is an internal VLAN with VLAN ID 4091, used for internal management communication among the hardware devices, like compute nodes, network switches. The same VLAN is used as a OpenShift® Provisioner Network. This VLAN is preconfigured in the factory and is immutable.
Internal Storage VLAN: It is an internal VLAN with VLAN ID 3201, used for the internal storage network. IBM Spectrum Scale uses this VLAN for their internal communication. This VLAN is preconfigured in the factory and is immutable.
OpenShift Customer VLAN: It is the VLAN configured during initial stage of the IBM Spectrum Fusion installation. This VLAN is used as the OpenShift Bare Metal Network.
Native VLAN: A Default Native VLAN with ID 1 configured is available. This ID is the PVID or Native VLAN for the links that are connected from the high-speed switch to the lab switch. Administrator can create a different Native VLAN and assign as PVID to the links.

Note: The list of reserved VLANs are as follows:

VLAN 4091 for Provisioning network
VLAN 3201 for Spectrum scale 100G Network
VLANs 3800-3999 reserved by switches

You must not create OpenShift customer VLAN (Bare Metal VLAN), Native VLAN and IBM Cloud® Satellite VLAN using these IDs.

Aggregate links

Links

Link aggregation is to combine multiple network connections in parallel.

Note: LACP is the preferred choice. Support is not available for non-LACP.

LACP: The standard-based negotiation protocol, which is known as IEEE 802.1ax Link Aggregation Control Protocol (LACP), is a way to dynamically build an Etherchannel.
No aggregation: If aggregation is not possible, this method is available, but not suggested, to provide high availability with no aggregation. With this method, you must enable Spanning Tree in customer switch or high-speed switch to avoid loops.
Note: For example, if you intend to use a switch pair that does not support Virtual Port Channel (VPC) or VLAG/CLAG, you can use this option to achieve network redundancy.

Network topologies

The topologies for network configuration are described as follows. In each figure, the high-speed switch is a part of the external client network outside of the system.

LACP topology: Note: LACP is the preferred choice. Support is not available for non-LACP.

In LACP topology, a single cable is connected to each high-speed switch. MLAG provides the capability to group multiple links to achieve high availability, redundancy, and increased throughput. The ports are grouped into a single LACP Port Group across two high-speed switches. Similarly, a single LACP port group must be created on connected switches.

Figure 1. LACP topology
No aggregation topology: In a no aggregation topology, one cable is connected to each high-speed switch. Because a potential for network loops is available in this configuration, a spanning-tree method is needed.
Note: LACP is the preferred choice. Support is not available for non-LACP.

Figure 2. No aggregation topology