Difference on DNS resolving between GUI and CLI

[fbantgat7]

Hi All,

A particular domain, let's call it "www.example.com" which is not configured as a CNAME but has an A record, fails to resolve on the CLI:

Code Select Expand

$ host www.example.com
Host www.example.com not found: 3(NXDOMAIN)

but resolves on the ISP's resolvers when using the [Interfaces: Diagnostics: DNS Lookup] on the router's GUI.

The router's /etc/resolv.conf shows:

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# cat /etc/resolv.conf
domain localdomain
nameserver 127.0.0.1
nameserver [ISP's resolver IPv4 address 1]
nameserver [ISP's resolver IPv4 address 2]
nameserver [ISP's resolver IPv6 address 1]
nameserver [ISP's resolver IPv6 address 2]
search localdomain

The PC's on the LAN also fail to resolve:

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$ nslookup www.example.com 192.168.1.1
Server: 192.168.1.1
Address: 192.168.1.1#53

** server can't find www.example.com: NXDOMAIN

This does not happen with other domain names, or even with the apex "example.com", these are resolved normally.  Just to confuse matters this problem occurs sporadically.  If I run a few times 'dig +trace +short www.example.com A'  on the PC, then I can obtain an IP address both on the PC and on the router's CLI.  A day or two later caches are flushed and the problem returns.

Why does this difference between GUI and CLI happen and how can I troubleshoot it?