Balance 710 - Not Passing DNS servers for DHCP connections

I am experiencing an issue where our Balance 710 is not passing DNS to DHCP clients. We have had this issue in the past with older firmwares, but it is super prevalent on firmware 8.1.1.

I’ve tried multiple settings, but ultimately have to set each client to static DNS to make them function.

Here is a snapshot of my LAN settings. I’ve tried with all the boxes checked and unchecked in different orders:

I have tried setting for WAN to pass DNS, setting DNS to static using 1.1.1.1 and 8.8.8.8.

Thoughts?

Does it work with “Assign DNS server automatically” unchecked, and the desired DNS servers for LAN clients entered in the DHCP server settings?

Negative. It still is not passing DNS to clients with the Assign DNS Server Automatically unchecked and specifying the settings.

Settings saved and applied of course.

Tested on two units, one wireless and one Ethernet. Both failed to acquire DNS.

For grins I have also tried enabling the DNS resolvers to see if I get any changes. I have tried enabling on all ports and just one. No changes. This is very perplexing and I see others having similar issues, but most of them are trying to run a local DNS server not use internal.

With the DNS proxy disabled, changing DNS resolvers will not do anything. Do LAN clients get the Balance IP address for DNS?

No that is the issue, no clients receive a DNS from the Balance.

@EM724,

We may need your help to perform the packet capture and verify the DHCP payload for the IP address info and the DNS server info released by the Balance 710. Do you think you can help on this ? This will help to verify whether the DNS info is released

Test Steps:

  1. Start the packet capture tool in the test PC.
  2. Connect the Ethernet cable to the network (Switch)
  3. Make sure the PC is able to obtained a IP from the network
  4. Save the captured results.

After that can you please attach the capture results in the ticket for us to check ?

Replied to your ticket directly.

Just an update that there was a unknown DHCP server in the LAN network that cause the issue. The unknown DHCP server intercepted the DHCP released from B710 and overwritten DNS server IP.

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I want to thank @sitloongs for his help in identifying the issue. While we thought for sure it was an issue with Peplink firmware, they were gracious enough to provide us a direction to look. It turns out another vendor for a radio interoperability product we use had a server running with Virtual Clients. They were using DHCP to send these virtual clients an IP address and after much pushing agreed to look at their system. As it turns out they failed to commit a table of saved changes to their hardware and it was intercepting or broadcasting DNS information out to the entire network. Kudos to Peplink team for going the extra step to assist us.

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