Intermittent connection on switch port

[Eddy_X]

I have a MS250 with all default settings connects to our network as a access lay switch.

The PC with firewall software has two NICs. One to the MRI machine within its own 172.x.x.x network, and the other one connects to our 10.x.x.x network. The firewall software does NAT to allow the MRI machine to communicate with other systems in our network. 

Connections between switches(Cisco-Meraki, Meraki-Meraki) are Trunk ports, allow ALL VLANs, and native VLAN1.

When I plug the firewall PC into MS250, I got intermittent ping success from MRI to VMWave.

When I plug the firewall PC into Cisco 2960, I got no problem. 

I was thinking maybe something to do with the ARP table since technically the NIC on the firewall PC which connects to my network will have two IP on the same MAC address. DAI is disabled by default and I tried to make all the trunking uplinks/downlinks ports trusted. Still having issues.

Any thought would be greatly appreciated. 

Edited1

Current Meraki MS firmware version MS11.27

Not sure if this has anything to do with this issue

[Russ_B]

Have you checked the logs on the switches when the Meraki switches are connected and the PINGs are failing? 

The first thing that comes to mind is that you may have a spanning-tree problem.  I remember reading something about having to use MSTP on Cisco Catalyst switches to avoid problems when connecting Meraki switches, but can't find it to link at the moment.  You might try turning spanning-tree off for a test, if that fixes the issue you'll know where to look.

Found the article I was looking for:

Advanced MS Setup Guide - Cisco Meraki

After re-reading the section on PVST/PVST+ it doesn't seem likely that is the cause of your issue, but it is probably worth checking.  The Event Logs on the Meraki switches should also be helpful.

[cmr]

@Eddy_X were you getting 10-15 success, then 30-60 seconds of failure in a repeated pattern?  We had that when we tried 12.28 on some MR355s where there were other Cisco IOS switches in the LAN.  We tried all the usual spanning tree fixes with support, but reverting to 14.21 firmware that support had asked us to downgrade from (along with some STP changes) fixed it.

Or is there a particular reason why you are running somewhat old (18 months+) firmware?