DNS issues with RUTXR1- maximum connections?

I have an RUTXR1 with approx 380 clients across two portbased VLANs on static addresses. A few DHCP.
I’m seeing a lot of failed address lookups on the client’s logs. " name does not resolve". It appears to be random across the clients so that at any one time there are a handful that are experiencing this. No other apparent pattern.
I note that the number of TCP connections to the RUT are in the 1300-1400 range. UDP around 500.
Is is possible that the RUT can’t handle the number of connections, and this is affecting the ability to server as a name server?
Each of the clients is configured to use the RUT as the DNS server (VLAN1 clients are using the RUT’s x.x.1.254 address, VLAN2 clients using the the x.x.2.254 address).

Am I on the right track here, and if so, how do I determine conclusively if the RUT is the bottleneck?
I am reluctant to change all the clients to some other external DNS.


While this was not tested with so many clients, but based on the number of TCP and UDP connections, I do not think that this is an issue. If you are using mobile connection on RUT, maybe the bandwidth is the issue? What is your WAN source?

By default, DNS on RUT acts as a DNS forwarder, i.e. it forwards DNS queries to the configured DNS servers. You can see what DNS servers are used via the following CLI/SSH command:

cat /tmp/resolv.conf.d/resolv.conf.auto

You can add DNS servers by navigating to Network → Interfaces → Edit LAN and specifying DNS servers there.

As an alternative, you can also push DNS servers to DHCP clients with DHCP option 6 in LAN → DHCP Server → Advanced settings.

Kind Regards,

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