Weird DNS Issues

[american_nisei]

On one of our networks, we have wireless client devices that when on the BIG SSID have no problems connecting to the Internet. However wireless devices on the SMALL or MEDIUM SSIDs are experiencing extremely slow access or no access to the Internet.

I tested pinging 8.8.8.8 and google.com from different wireless devices. When the wireless client is connect to BIG, both pings resolve quickly and respond with < 5MS response. When same devices are connected to SMALL or MEDIUM, then the 8.8.8.8 pings resolve quickly. But pings to google.com either time out or respond in 50 - 90 MS.

BIG and SMALL SSIDs utilize Meraki DHCP.   The MEDIUM SSID utilizes local NAT.  

Because of the performance issues for name resolution of "google.com", it seems like a weird DNS issue, but if DNS was the root cause, it seems like it would affect all SSIDs, but its only affecting two of three SSIDs.  

Any thoughts and/or suggestions?

[PhilipDAth · Accepted solution]

Do you have any bandwidth shaping configured?

Their have been several updates relating to DNS in Meraki, mostly to do with security advisories.  Try updating their firmware.

[american_nisei]

No bandwidth shaping configured.  The firmware for the security appliance, switches and AP are old...3 to 5 versions old.  Didn't necessiarily see much about DNS though, but will get the firmware upgrades a shot.

[BlakeRichardson]

Being its wireless related there could be a ton of variables.

1. Have you confirmed the issue happens on more than one AP

2. Have you restarted the AP?

3. Is there any difference in bands or how the network is setup.

4. What is congestion like on the network which is working properly compared to the affected networks? 

If your ping times are slow if you are pinging 8.8.8.8 then its not DNS related

[PaulRusso]

This sounds like a DHCP server configuration issue or an issue with your DNS server.

Wireless Configuration:

1. What mode do you have selected under Addressing and Traffic? (NAT mode, Bridge mode, L3 Roaming, L3 Roaming + Concentrator, or VPN) (Wireless > Access control)
2. Are you using VLAN Tagging? If so, are both SSIDs associated to the same VLAN? (Wireless > Access control)
3. Do you have any firewall/traffic shaping rules enforced on these subnets? Bandwidth limits defined? (Wireless > Firewall & Traffic Shaping)
4. What kind of devices connect to these SSIDs? How many?
5. Do you have any Network-wide group policies assigned by device type? (Wireless > Access control)

Servers:

1. Have you checked the DNS Server scope option on the DHCP server for the subnet(s) associated with the 2 SSIDs that are experiencing issues?
2. Have you checked the resource utilization on your DNS server(s) to make sure that your CPU and Memory are not being heavily utilized? (this was a culprit to a similar issue I experienced not too long ago...)

[DanielKritikos]

I too have DNS issues with meraki.

From my testing it is related to the option "use upstream DNS",

ISP DNS = pages load instantly

google or any other dns = pages load instantly.

Use upstream which broadcasts the gateway ip as the dns server and then sends the traffic upstreme to the ISP,s dns is where the issue lies.

If you are fortunate enough to not have any configs that are sec dependent on DNS, just change the dropdown on DHCP dns settings from Upstream to anything else. you can manually enter in one or I just selected use Googles Public

Problem solved.

But the actual problem is not really solved, there is still an issue with Meraki, case has been escalated.

Hope this helps

R
Dan