Computers won't reconnect to a different switch on the same network

[bit_transporter]

Greetings,

We are relatively new Meraki customers, and have deployed several MS250s as access switches across our various campuses this year.

Everything for the most part has been great. 

However, in one particular building, we are noticing some odd behavior. This building is all on the same VLAN and subnet. We have two stacks here (one with 6, one with 3). 

It seems anytime an end user on this network moves their computer to another desk, and consequently, to a different switch, they cannot reconnect to the network. We do see them obtain a DHCP config, but they cannot ping anything other than some devices on the LAN. Oddly, they cannot even ping their gateway. 

The only time when this has been successful is when the user moves close by and remains on the same switch.

We tested by plugging in a brand new computer to the same "problematic" switch and it worked just fine.

Our hypothesis is that once a device MAC has joined a switch, it does not work when connecting to a different switch. It feels to me like MAC tables aren't updating properly. 

My next action will probably be rebooting the switch, but we can only do this after hours. I am a little concerned about what behavior a reboot would trigger.

Has anyone experienced an issue of this nature? Or does anyone have a recommended course of action they would take in this case? 

TIA for any insight you could provide. 

[GreenMan]

Did you raise a Support case for this?

[bit_transporter]

Hi,

I have not yet, but that is on my list.

Edit: Case has been opened. I'll leave this thread open too in case someone has some insight here.

[GreenMan]

I think you'll need to do that.   Recommend you maybe create a case via Dashboard with any attached pcaps you have etc. in advance - but then call in, quoting the case ref, for some live troubleshooting with a client affected by the issue in real time.

[bit_transporter]

Thanks, just raised a case with support via the Dashboard.

[GIB_NW]

Hello
You have two stacks ( one 6 and one 3 stack) - Assuming these are in different locations in the same building?
How are the two stacks connected?
Do you have a Distribution switch between the two stacks ?
Or are both Stacks connected to each other ?

For the ports that your users connect to are these Trunk or Access ports?
Are your inter-switch ports all Trunk ports?

What is do you use for your Layer 3 routing for these two stack switches ?

[bit_transporter]

These two stacks are in the same building, and in the same closet, but they are not connected directly. We use physical stacking cables to combine the switches into a stack.

Both stacks uplink via their own LACP bundles to the same access aggregation switch. Since both stacks are on the same VLAN there is no routing between them. Any other routing is done upstream on a firewall. 

User connected ports are access ports.

All inter-switch ports are trunks.

[redsector]

I had this issue with small unmanaged switches connected to the Meraki or Cisco Cat switches: if you once connected a computer to this small switch it keeps the MAC address and connecting the computer somewhere else is causes no network connection ... until you reboot the small unmanaged switch. I had this also with IP-phones, when you connect the computer to the IP-phone the phone is working like an small switch, it´s keeping the MAC-address of the computer and if you try to connect the computer somewhere else it can´t use the network.

[bit_transporter]

We don't have any small unmanaged switches in the equation, but that is very interesting.

[redsector]

The solution for this problem with the MAC-addresses was so set this commands on the Cisco Catalyst ports (with IP-phones with inbuilt switch and other unmanaged switches connected to Cisco Catalyst switches):

switchport port-security aging time 2
switchport port-security aging type inactivity

So, the switch forgets the MAC addresses on this port after 2 minutes. Then you can plug the devices to another place and it works.

Since then I didn´t had this problem, and I don´t know if Meraki MS switches handels this otherwise, because for them I don´t have an "forget MAC addresses" command.