SG350X - split stack gives duplicate IP

[RohDevelopment]

Hi all,

in my setup I have two SG350X switches stacked with one CAT6 cable in a chain configuration. In my research I was testing different scenarios, among which is the failure of this cable, port or SFP (if I would use a fiber stacking cable).

Simulating this by extracting the cable I noticed that both switches become master as expected. They are connected to a root switch via RSTP. However, both keep the same IP address, which results in a duplicate IP address. The strange thing is that I can connect to their Web GUI's when I connect my laptop to the individual switches. I can also ping the root switch via both former stacked switches.

Can someone give me some more information on this?

Kind regards,

[Seb Rupik]

Hi there,

The reason you can access the local attached switch will because that switch will process the packet destined to it management IP and handle it accordingly.  This makes the assumption that your ‘user’ VLAN uses the same subnet as the management IP. If your user VLAN and management VLAN was routed on the ‘root switch’ then you may end up connecting to a different SG350 each time, depending on the state of the ARP and MAC table.

Regarding being able to ping to the root switch, when your packet arrives on the root switch it will update its ARP and MAC table with the  source SG350 management MAC address. The reply will then be sent down the attached switchport to the SG350 which originated the ping.

If you were pinging from both switches at the same time to the root switch, you may get different results!

Cheers,

Seb.

[RohDevelopment]

Dear Seb,

thank you for your answer and the explanation. I indeed have one VLAN setup, and will do some tests with two VLANs to check if that will help.

Pinging with two devices on both switches at the same time is going fine however! The connection stays successfull.