See ClusterXL Administration Guide R80.20:
We recommend that you secure the synchronization interfaces using one of the following strategies:
• Use a dedicated synchronization network.
• Connecting the physical network interfaces of the Cluster Members directly using a cross-cable. In a cluster with three or more members, use a dedicated hub or switch.
Notes:
• See Supported Topologies for Synchronization Network (on page 26).
• You can synchronize members across a WAN. To do this, do the steps in Synchronizing Clusters on a WAN (on page 54).
• In ClusterXL, the synchronization network is supported on the lowest VLAN tag of a VLAN interface. For example, if three VLANs with tags 10, 20 and 30 are configured on interface eth1, only interface eth1.10 may be used for synchronization.
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