3Com Switch 4500 Family Manual page 571

To reduce the risk of being attacked by malicious users against opened socket and enhance switch
security, the Switch 4500 series Ethernet switches provide the following functions, so that a cluster
socket is opened only when it is needed:
Opening UDP port 40000 (used for cluster) only when the cluster function is implemented,
Closing UDP port 40000 at the same time when the cluster function is closed.
On the management device, the preceding functions are implemented as follows:
When you create a cluster by using the build or auto-build command, UDP port 40000 is opened
at the same time.
When you remove a cluster by using the undo build or undo cluster enable command, UDP port
40000 is closed at the same time.
On member devices, the preceding functions are implemented as follows:
When you execute the add-member command on the management device to add a candidate
device to a cluster, the candidate device changes to a member device and its UDP port 40000 is
opened at the same time.
When you execute the auto-build command on the management device to have the system
automatically add candidate devices to a cluster, the candidate devices change to member devices
and their UDP port 40000 is opened at the same time.
When you execute the administrator-address command on a device, the device's UDP port
40000 is opened at the same time.
When you execute the delete-member command on the management device to remove a
member device from a cluster, the member device's UDP port 40000 is closed at the same time.
When you execute the undo build command on the management device to remove a cluster, UDP
port 40000 of all the member devices in the cluster is closed at the same time.
When you execute the undo administrator-address command on a member device, UDP port
40000 of the member device is closed at the same time.
Examples
# Configure the current switch as a management device and set the cluster name to aaa.
<Sysname> system-view
System View: return to User View with Ctrl+Z
[Sysname] cluster
[Sysname-cluster] build aaa
There is no base topology, if set up from local flash file?(Y/N)
n
#Apr 3 08:15:03:166 2000 aaa_0. 4500 CLST/5/Cluster_Trap:- 1 -
OID:1.3.6.1.4.1.2011.6.7.1.0.3(hgmpMemberStatusChange):member 00.00.00.00.00.12.
a9.90.22.40 role change, NTDPIndex:0.00.00.00.00.00.12.a9.90.22.40, Role:1
[aaa_0.Sysname-cluster]
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