When VLAN IDs are entered in the Global VLAN Configuration or in the Port VLAN Configuration on a GS-3xxx series switch, an own entry is created for each switch port and each VLAN ID in the VLAN membership table. If a great amount of VLAN IDs are entered and the ports or VLANs are monitored via SNMP, this causes the CPU load to increase dramatically and the switch to respond with a delay.
This article describes how this behaviour can be avoided.
1) Modifying the "Allowed Access VLANs" in the "Global VLAN Configuration":
1.1) Go to the menu VLAN Management → VLAN Configuration.
1.2) Under Global VLAN Configuration only VLAN IDs must be entered in the field Allowed Access VLANs, which are assigned to a port with the tagging mode Access (in this example the VLAN IDs 1,2 and 5).
Under no circumstances should all VLAN IDs from 1-4094 be entered in the field "Allowed Access VLANs", as this would lead to the behaviour described above!
2) Modifying the "Allowed VLANs" in the "Port VLAN Configuration":
2.1) Go to the menu VLAN Management → VLAN Configuration.
2.2) Under Port VLAN Configuration the Allowed VLANs are set to 1-4094 automatically (default setting) when setting the Mode to Hybrid or Trunk, which can lead to the behaviour described above.
It is currently in review if the default setting for Allowed VLANs can be changed to 1.
2.3) Therefore modify the field Allowed VLANs, so that only the used VLANs are entered (in this example the VLAN IDs 1,2 and 5).