Maintaining gateway connection on a Backup domain controller

Mikejett
Mikejett used Ask the Experts™
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We are loosing Internet access when our Small Business Server 2011 Standard is down or rebooting for updates.  I have a backup domain controller, yet internet access still goes down. Whats the best option to configure my backup domain controller to maintain the connection?
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Adam BrownSenior Systems Admin
Top Expert 2010

Commented:
Configure DHCP to point clients to both servers.

Author

Commented:
Should the backup controller have DHCP installed and running as well?
Adam BrownSenior Systems Admin
Top Expert 2010

Commented:
no. Only one DHCP server per subnet is allowed and SBS doesn't have the ability to do redundant DHCP servers. Clients will retain their last DHCP assigned address as long as they remain online.
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This sounds like a gateway address problem.
What gateway address is the backup DC using?
If it's using the main DC, then it's all explainable because when that's offline, there will be no gateway.
I would likely point the backup DC to the internet gateway as "gateway" address.

Unless the backup DC doesn't have an IP address, I don't see what DHCP has to do with this....

Author

Commented:
Still trying to make sense of this. how would I go about to "Configure DHCP to point clients to both servers"?

Could this potentially be a DNS issue if all clients point to the SBS for DNS and the DNS is the ip address of the SBS machine?  The reason I say this, I would expect the address to be valid until it needs to be renewed under DHCP.
kevinhsiehNetwork Engineer

Commented:
Your DHCP clients needs DNS entries for both DCs. If only using SBS server for DNS that won't work when that server is down.

Author

Commented:
I have the gateway IP address on the backup controller listed.  Under DNS, It does point to the IP of the DC for DNS resolution also outside secondary IP address as well.
I think you are on the right path.
Do you have both servers configured as DNS servers on clients network adapters?
You can easily check if it is DNS problem. When SBS is down, try to ping external IP address from client (like google's DNS servers at 8.8.8.8) and try to ping some external hostname (like www.hp.com). If ping to IP works, and ping to hostname doesn't resolve, then it is DNS problem.
If ping to both addresses fails, then it is connectivity problem.

Author

Commented:
Davorin,

I added the backup domain controller to the DHCP scope on the primary SBS server.  I then restarted DNS server.

For a test, my working station is obtaining both IP and DNS from the server.

After rebooting server, I lost internet connection.  I am able to ping external IP addresses, just no gateway.  I then manually added the IPs for both primary and secondary server to my NIC and the connection restored.

It looks like by just adding the secondary DNS server IP to the DHCP server didn't resolve still.  

Anything else I should do to ensure clients that obtion DNS automatically  from the server automatically will resolve to backup DNS?
kevinhsiehNetwork Engineer

Commented:
"Under DNS, It does point to the IP of the DC for DNS resolution also outside secondary IP address as well."
Where is this? On the DC, or client?

No AD domain joined device should be using any outside DNS server. You need to resolve your AD domain for AD to work properly and reliably.
Make sure that the additional DC can do name resolution when the SBS server is offline. The additional DC should use the SBS server for primary DNS, and use itself for secondary DNS. In addition, in the DNS Server properties, you should probably have forwarders configured. I use OpenDNS 208.67.222.222 and 208.86.220.220.
kevinhsiehNetwork Engineer

Commented:
Post output of "ipconfig /all" from a client.
On your DHCP server you should have listed in DHCP > IPv4 > Scope > Scope Options > 006 DNS Servers both your servers - sbs and second domain controller IP addresses. You don't need to restart DNS server. You need to restart client (or do ipconfig /release and then ipconfig /renew) to optain new configuration data from DHCP server (assuming you have set client network configuration to automatic and not manual).

You can check current ip configuration of the cleint with ipconfig /all and under network adapter DNS configuration you should have listed both of your servers.

Author

Commented:
So I reverted the client back to obtaining DNS automatically and releasing and renewing the IP and the IPs now appear for DNS.  Thanks!

Author

Commented:
Thanks Kevinhsieh and Davorin.  Both of your responses help resolve my issue.
You are welcome. I'm glad your problem is solved.

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