GS1900 tagged VLAN nodes drop off after 5 minutes

Hi @Zyxel_Judy I did some further tests with your advice

GS1900-24 uplinked to a live LAN but only hosting test PCs itself.
In all cases below, the switch MAC table looks correct, it contains all the hosts connected to the switch itself, and those from the rest of the LAN.

HP and Asus pinging each other
Untagged: Pings stay up for over 3 hours, I stopped timing after that.
Port-based VLAN ID2: Pings stay up for over 3 hours, I stopped timing after that also.

Tagged VLAN ID3: Pings stop after less than 5 minutes. Interestingly, on the most recent test, the Asus stopped responding to HP, but HP continued to respond to Asus.

This is the HP ARP table before and after Asus stopped responding to ping (but HP continued responding to Asus). The Asus 192.168.0.16 remains in the ARP table.

C:\Users\5CD0172J00>arp -a
Interface: 192.168.0.15 --- 0x6  Internet Address      Physical Address      Type
192.168.0.16          50-46-5d-3f-10-bf     dynamic
192.168.0.255         ff-ff-ff-ff-ff-ff     static
224.0.0.22            01-00-5e-00-00-16     static
224.0.0.113           01-00-5e-00-00-71     static
224.0.0.251           01-00-5e-00-00-fb     static
224.0.0.252           01-00-5e-00-00-fc     static
239.255.255.250       01-00-5e-7f-ff-fa     static

C:\Users\5CD0172J00>arp -a
Interface: 192.168.0.15 --- 0x6  Internet Address      Physical Address      Type
192.168.0.16          50-46-5d-3f-10-bf     dynamic
192.168.0.255         ff-ff-ff-ff-ff-ff     static
224.0.0.2             01-00-5e-00-00-02     static
224.0.0.22            01-00-5e-00-00-16     static
224.0.0.113           01-00-5e-00-00-71     static
224.0.0.251           01-00-5e-00-00-fb     static
224.0.0.252           01-00-5e-00-00-fc     static
239.255.255.250       01-00-5e-7f-ff-fa     static


At the other end, this is the Asus ARP table before and after Asus stopped responding to HP (but HP continued responding to Asus). HP 192.168.0.15 disappears from the ARP table.

C:\Users\Gonzales>arp -a
Interface: 192.168.0.16 --- 0x12  Internet Address      Physical Address      Type
192.168.0.15          b0-5c-da-29-96-02     dynamic
192.168.0.255         ff-ff-ff-ff-ff-ff     static
224.0.0.22            01-00-5e-00-00-16     static
224.0.0.251           01-00-5e-00-00-fb     static
224.0.0.252           01-00-5e-00-00-fc     static

C:\Users\Gonzales>arp -a
Interface: 192.168.0.16 --- 0x12  Internet Address      Physical Address      Type
192.168.0.255         ff-ff-ff-ff-ff-ff     static
224.0.0.22            01-00-5e-00-00-16     static
224.0.0.251           01-00-5e-00-00-fb     static
224.0.0.252           01-00-5e-00-00-fc     static

I then added a third test PC, a Fujitsu Esprimo desktop 192.168.0.31 - all three test PCs have Realtek network host adapters (although at this point not sure if exactly the same model).

HP and Fujitsu pinging each other on VLAN ID: 3 stayed up for over 3 hours. ARP tables on both showed each other's IP and MACs.

Then I added Asus into the test also on VLAN ID 3.
HP and Asus pinging each other
Fujitsu and Asus pinging each other

Pings between HP and Fujitsu continued to stay up, over 5 hours at the last check
Pings between Asus and the other two dropped after 2 minutes.

Before the ping drop, all three test PCs had correct ARP tables.After the ping drop, Asus dropped all ARP entries, while HP and Fujitsu retained the entries from each other's peers.

From this test, I would say I'm satisfied that the ZyXEL switches are performing as they should, and the problem is with Windows on the Asus laptop. It is strange, though, how the pings stay up longer (approximately 1.5 hours) if the switch is isolated from any LAN.