Should a workgroup be configured with a DNS suffix Search List

Question

I bought a new Linksys Mesh router a few months ago. This was to replace a router that was quite a bit past its prime, and I had just got upgraded ISP service to 600 mbps (from 60mbps). Since that time I have had intermittent connection issues that seem to be, in some cases, DNS related ( Server not found errors while browsing). When this happened a NSLOOKUP request failed with a timeout. Configuring the ISP's DNS addresses on the LAN side seem to make that issue go away.

When I capture Wireshark traces what I'm seeing is not quite making sense. I hope to learn if this is correct and normal.

I am on a Windows 10 system that has all the latest updates installed. On the LAN side I have a switch with port mirroring monitoring the Ethernet connection port to the router. On the WAN side I have another switch with port mirroring monitoring the WAN side. I am using Wireshark to capture the traces.

First I noticed that a look at the output from ipconfig /all shows a Connection-specific DNS Suffix Search List entry that is obviously my ISP's domain. Since my home network is configured as a workgroup, should the DHCP service in the router be setting this? What are the ramification of this being set?

I am also seeing is the router sending DNS requests to the ISP's servers for nodes on my local network.

1. A node on my network sends a DNS A and AAAA request to the router with the DNS suffix attached.
2. Meanwhile on the WAN side I see 4 Type AAAA requests, one to each of the 4 DNS server address configured, 2 IPv4, 2 IPv6.
3. All of which receive a response of 'No such name."
4. The router sends back a Type A response with the IPv4 address, and a Normal Type AAAA response with no answers data.
5. Sometimes the router will send back a ICMP message to the server of Port Unavailable. I assume this is due to the router closing the port.

I can provide a link to the trace files if needed. I don't know the process of providing trace files on this site. Any help understanding what's going on is welcome. There are other anomalies in my traces but lets deal with one issue at a time.

I'm thinking that the router's DNS behavior is at best messy, worst, incorrect. Thanks for any help you can provide.

Answer 1

If it helps, I can share some of my home network settings.

I am also seeing is the router sending DNS requests to the ISP's servers for nodes on my local network.

I don't think that it should be doing that. If your router is providing DHCP services then it should resolve local names.

My laptop is configured for DHCP and I see that I have a connection specific suffix of "home".

Wireless LAN adapter Wi-Fi:  
  
   Connection-specific DNS Suffix  . : home  
   IPv6 Address. . . . . . . . . . . : fd00::cb5:4656:33f2:7725  
   Temporary IPv6 Address. . . . . . : fd00::8091:2fcf:43c7:b342  
   Link-local IPv6 Address . . . . . : fe80::cb5:4656:33f2:7725%21  
   IPv4 Address. . . . . . . . . . . : 192.168.1.6  
   Subnet Mask . . . . . . . . . . . : 255.255.255.0  
   Default Gateway . . . . . . . . . : 192.168.1.1  

In the network settings of my router, I found that in a System Settings tab.

I see that names resolve with the .home suffix.

C:\>nslookup 192.168.1.7  
Server:  Wireless_Broadband_Router.home  
Address:  192.168.1.1  
  
Name:    Test10.home  
Address:  192.168.1.7  
  
  
C:\>ping -n 1 test10  
  
Pinging test10.home [192.168.1.7] with 32 bytes of data:  
Reply from 192.168.1.7: bytes=32 time<1ms TTL=128  
  
Ping statistics for 192.168.1.7:  
    Packets: Sent = 1, Received = 1, Lost = 0 (0% loss),  
Approximate round trip times in milli-seconds:  
    Minimum = 0ms, Maximum = 0ms, Average = 0ms  
  
C:\>   

In my router's web interface, there is a page for "My Network". It lists my pc's, phone's, and the STB's for my TV's, and shows the IP addresses allocated to each device.

The final answer may depend on how your router works. Or on how it's configured. If you do an nslookup on a local IP address, that should resolve to the local name. You may need to contact your ISP's support team for help.

Answer 2

Thank you for the information. That's what I was gathering from other posts. I think the router is mucking it up because I can't configure that parameter on my router.