DC sync issues causing DNS broadband surfing problems?

[TCTC]

Hi

 

Has anyone ever experienced problems browsing the internet caused by DC sync issues?

 

We’re unable to browse the internet and receiving DNS errors but so far our internet provider have not identified any issues although tests are continuing.

 

In the meantime I’ve checked DC event logs and there are references that the DC hasn’t synced and AD DS but I don’t know if this is linked.

 

How can I confirm both DCs are synced? Can this be done manually?

 

Thanks

[PeterH]

DC replication issues are unlikely to cause DNS errors but they may well be caused BY DNS errors.

 

If DNS is not working properly on your domain then you will have issues with replication between the DCs

 

First check the DNS server is running on all your DCs

 

On a PC, check if you can resolve internet names e.g. by doing ping Google

 

If it says it can't find host, then check what your DNS server is set to - ipconfig /all

 

You can try querying a DNS sever directly, for example to check your internal DNS is able to resolve names you might do:

 

nslookup google.com 192.168.0.9

 

Where 192.168.0.9 is the address of your DNS server....you should get a "non-authoritative answer" google.com and an address. If you get DNS request time out check if your DNS server is running OK

 

If that doesn't work try nslookup google.com 8.8.8.8

 

If that works and the 192.168.0.9 one doesn't then you've got problem with DNS forwarders or root hints. Check your DNS server has Internet connectivity.

 

If neither of those work then you've got basic internet connectivity problems

 

DC replication errors are unlikely to cause problems accessing the Internet, but they WILL cause other major problems on your network so they need to be sorted urgently.

[TCTC]

Thanks for that. It’s definitely a DNS issue but don’t know why it’s failed all of a sudden.

 

I can ping clients and servers in both directions but unable to browse internet.

 

Any advise with DNS forwarders or root hints?

 

The DNS Servers (DCs) are unable to access the internet as well and I get the ‘no internet connection’ on the network adapter

 

Our clients don’t get this message.

 

Thanks

[PeterH]

If the DNS servers are unable to access the Internet then that's probably why the clients can't as well.

 

On your DCs, first thing is to check that the default gateway is reachable. For example ping 192.168.0.1 should get replies from 192.168.0.1. If that doesn't work then check if your router is switched on, connected to the LAN, tried restarting it? It depends how you connect to the Internet, any firewall, Smoothwall or similar?

 

If that works, then try ping an external ip address such as 8.8.8.8 which should always get a reply. If not then tracert 8.8.8.8 might show where the connection is failing.

 

The DNS forwarders are configured in the DNS Management Console in the Server properties on the Forwarders tab. There may not be any listed. If not it is supposed to use the root hints (you should see a list of servers and ip addresses on that tab).

[TCTC]

Thanks for your replies.

 

It turns out it was Schools Broadband's DNS Servers causing the problems. Downtime was 24 hours so I was panicking thinking it was us but other schools had problems as well.