I have a client which recently started having issues with their internet connectivity. I have been trying to figure out what might be the cause but am coming up empty. I think it might be a DNS issue on the the domain controller but may be something else. When I try to Ping a website (yahoo.com) from the controller it has quite a bit a latency and when I go to Whatsmyspeed.com and finally get to the site, need to request twice, it shows the ping as being 24ms and their download speed as 10Mbps which is what is should be but the connectivity is not right which leads me to think there is something wrong with the DNS. I have ran nslookup and it points to the Domain controller yet when I run nslookup google.com <server IP> I get the controller name.domain and the address then a non-authoritative answer that states the DNS request timed out. Timeout was 2 seconds then it returns the site name and address(s).
First how can I see if it is a server issue?
Second how can I see if it is an ISP issue?
Maybe it is the router firewall but don't know where to start. This all started with Sonos not working on the network.
Thanks in advance for your help.