Some modern switches drop DECnet and cluster (SCS) packets.  Older Cisco Catalyst 4000 series switches were infamous for this.  Often, when a switch gets busy, it will prioritize traffic and start dropping packets it does not recognize.  Many modern switches do not recognize SCS and DECnet packets.

If you encounter this problem, try the following solutions:

•If using a managed switch, limit speeds to 10/100 on the port assigned to the Avanti NIC.

•If using an unmanaged gigabit switch, try replacing it with a 10/100 switch.

•If the first two options do not work, try substituting a different switch brand or model.

In-house, we have had good luck with Netgear, Linksys, and HP Procurve equipment.  However, we have had issues with Netgear gigabit equipment in clustered environments.  Cisco and Netgear 10/100 switches have worked well with clusters.