Hey all, so we have this problem in a network where we have Meraki MX and behind MX Meraki switches and behind those HP / cisco etc. switches and many Meraki and Ruckus APs in a hotel This is the 2nd time this has happened, when a group of usually Americans come and start hosting meetings all the Meraki switches start going into Disabled switch (bad DNS) mode and what happens is that anyone connected to any switches or APs behind them has working DNS, so basically "no internet access", even though the actual VLANs are using different DNS addresses on different VLANs than the switches management etc. Disabled switch (bad DNS) occurs every 10-15 minutes and stays for 2-5 in Disabled switch (bad DNS) mode and while in Disabled switch (bad DNS) mode, no DNS queries work so the customer says "no internet access" Close up of the pumping DNS: - I found nothing unusual from clients or traffic, except maybe 20-40 clients connecting to their VPN - I have swapped the switched management DNS settings from ISP -> Google -> Internal but the problem persists - I have switches management static and DHCP but the problem persists - I have changed switch MTU from default to 1500 but the problem persists - I found no other DHCP servers within the network - I found no new devices connected to LAN via ethernet, so it must be via WLAN (Ruckus and/or Meraki MR) - I disabled RSTP on Ruckus AP ports but the problem persists - I have tried IGMP snooping and flood unkown multicast traffic enabled / disabled but the problem persists - Firmwares are up to date and meraki support has gone through the settings and found nothing, only that it is "ISP problem", which it is not. Problem starts and ends as soon as the group starts working. So what seems to happen is something is causing all of the DNS traffic to pump in 10-15 minute cycles and it seems to affect only up to switches (MS-220 series) (not MX) and everything behind switches. Management VLAN 2 (where the switches are) and also all traffic VLANs. Has anyone come across this or anything like it?
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