Big trouble with UCS as DNS Server

UCS - Univention Corporate Server
1

I configured UCS as internal DC Master & DNS Server, but i can’t reach out external sites; internet connection is very leak / slow after UCS is setup.

This also means that internal connections between other devices nas server, DC, file server are also slow where working is not possible.

There fore i disabled UCS as Server.

Here my configuration:

Unitymedia Router: xxx.xxxx.xxx.1
Unitymedia Router local DNS: xxx.xxxx.xxx.1
Unitymedia Router = DHCP

UCS: xxx.xxxx.xxx.254

  1. External DNS UCS: 127.0.0.1
  2. External DNS UCS: 82.69.88.12 (External DNS from Unitymedia Router)
  3. External DNS UCS: 82.69.89.1 (External DNS from Unitymedia Router)

Router:
xxx.xxxx.xxx.1

I also tried with following DNS
2) 8.8.8.8
3) 8.8.4.4

The Windows clients uses:
DNS: xxx.xxxx.xxx.254
DHCP by Unitymedia Router

but same issue, internet connection is very slow, not reachable.

nslookup works well.

Any ideas how can I narrow down the error?

Would be nice if UCS could be established as an DC Master for my network.

kindly
adursun

2

Hi,
use your Windows PC for the following steps to narrow down the issue (I am pretty sure this is some sort of misunderstanding combined with configuration error).

Step 1: Check routing:

ping 9.9.9.9
Does it work? Fine.

Step 2: Check DHCP given settings

[...]
Ethernet-Adapter Ethernet 2:

   Verbindungsspezifisches DNS-Suffix: multi.ucs
[...]
   DHCP aktiviert. . . . . . . . . . : Ja
   IPv4-Adresse  . . . . . . . . . . : 192.168.92.140(Bevorzugt)
[...]
   Standardgateway . . . . . . . . . : 192.168.92.254
   DHCP-Server . . . . . . . . . . . : 192.168.92.10
[...]
   DNS-Server  . . . . . . . . . . . : 192.168.92.10
                                       192.168.92.254

In case you do not use your UCS server as DHCP server you should make sure your DHCP server gives the domain name of your local domain and (more important!) the IP address of your UCS server as DNS server! In the “DNS-Server” part you should NOT see any other servers except your UCS server!

Step 3: Check your DNS forwarder

To verify your local DNS forwarder (usually the IP of your router) is running fine ask him for any (non-local!) domain name.
Note: You can use multiple servers here instead of your local one. Your might want to use 9.9.9.9 or the given DNS-IP from your Internet provider.

C:\Users\user@multi.ucs>nslookup www.zdr.de 192.168.92.254
Server:  UnKnown
Address:  192.168.92.254

Nicht autorisierende Antwort:
Name:    www.zdr.de
Address:  91.195.240.126

Step 4: Verify settings on UCS

Please follow this article to verify the correct DNS settings. and use the IP address(es) from step 3 as dns/forwarder1 and dns/forwarder2

Step 5: Re-configure your DHCP server

Step 5a: Using non-UCS as DHCP

Change your settings on your DHCP server to tell the clients to use the IP of your UCS server instead of the one of the router (or DHCP server). If your clients do not use the UCS server as DNS server all your domain related functionality will fail for sure!

Step 5b: Use your UCS as DHCP

Configure your UCS DHCP according to the documentation.

Step 6: Re-load settings on Windows PC:

Run cmd.exed as Administrator and type:

ipconfig /release *
ipconfig /renew *

Your Windows PC should now use the UCS server as DNS server (see Step 1).

Done

In case you are still having issues, look for DHCP troubleshooting tips.

/CV