3.3 LAN Connectivity Guidelines

The primary objective of LAN connectivity in a cluster is to provide uninterrupted heartbeat communications. Use the guidelines in this section to design the LAN connectivity for each of the peer clusters in the business continuity cluster:

3.3.1 VLAN

Use a dedicated VLAN (virtual local area network) for each cluster.

The cluster protocol is non-routable, so you cannot direct communications to specific IP addresses. Using a VLAN for the cluster nodes provides a protected environment for the heartbeat process and ensures that heartbeat packets are exchanged only between the nodes of a given cluster.

When using a VLAN, no foreign host can interfere with the heartbeat. For example, it avoids broadcast storms that slow traffic and result in false split-brain abends.

3.3.2 Channel Bonding

Use channel bonding for adapters for LAN fault tolerance. Channel bonding combines Ethernet interfaces on a host computer for redundancy or increased throughput. It helps increase the availability of an individual cluster node, which helps avoid or reduce the occurrences of failover caused by slow LAN traffic. For information, see /usr/src/linux/Documentation/bonding.txt.

When configuring Spanning Tree Protocol (STP), ensure that Portfast is enabled, or consider Rapid Spanning Tree. The default settings for STP inhibit the heartbeat for over 30 seconds whenever there is a change in link status. Test your STP configuration with Novell Cluster Services running to make sure that a node is not cast out of the cluster when a broken link is restored.

Consider connecting cluster nodes to access switches for fault tolerance.

3.3.3 IP Addresses

Use a dedicated IP address range for each cluster. You need a unique static IP address for each of the following components of each peer cluster:

  • Cluster (master IP address)

  • Cluster nodes

  • Cluster resources that are not BCC-enabled (file system resources and service resources such as DHCP, DNS, SLP, FTP, and so on)

  • Cluster resources that are BCC-enabled (file system resources and service resources such as DHCP, DNS, SLP, FTP, and so on)

Plan your IP address assignment so that it is consistently applied across all peer clusters. Provide an IP address range with sufficient addresses for each cluster.

3.3.4 Name Resolution

In BCC 1.1 and later, the master IP addresses are stored in the NCS:BCC Peers attribute. Ensure that SLP is properly configured for name resolution.

3.3.5 IP Addresses for BCC-Enabled Cluster Resources

Use dedicated IP address ranges for BCC-enabled cluster resources. With careful planning, the IP address and the name of the virtual server for the cluster resource never need to change.

The IP address of an inbound cluster resource is transformed to use an IP address in the same subnet of the peer cluster where it is being cluster migrated. You define the transformation rules to accomplish this by using the Identity Manager driver’s search and replace functionality. The transformation rules are easier to define and remember when you use strict IP address assignment, such as using the third octet to identify the subnet of the peer cluster.

For an example of configuring a dynamic transformation by using DNS, see Section E.0, Using Dynamic DNS with BCC 1.2.