NBAR Blocking DNS for a PC

[Bala1]

I see this error on MX 

Source IP: 192.168.128.55, Source Port: 43467, Destination IP: 9.9.9.10  « hide

Destination Port	53
Protocol	UDP
Block Type	DNS
NBAR ID	3086
Classification
Layer 7 firewall rule	Deny

Category : NBAR

Event Type : Layer 7 rule

is there anyway to unblock or allow this? Blocking DNS like this is a headscratcher ? Any help would be appreciated.

[alemabrahao]

Don't you have any layer 7 firewall rule blocking it?

Can you show your firewall configuration please?

[Bala1]

I do. I’m blocking all Advertising and some countries. 

[Brash · Accepted solution]

Your Layer 7 firewall rules have detected and blocked a DNS request based on NBAR ID 3086 (OpenX Advertising).

The blocking of the DNS request is part of the Meraki MX functionality.

NOTE: DNS traffic (TCP/UDP Port 53) may also get blocked by Layer 7 rules if it contains a query for a domain the rule in question covers.

For example, you may see a block on UDP port 53 classified as "abc.com" if the "All News" rule is configured on Dashboard, and a user device sends a DNS query for said domain. 

Mapping Layer 7 Firewall Rules to NBAR IDs - Cisco Meraki

[Bala1]

Ah ok. This must be it. Thanks for the quick response.