Performing DNS queries through my local UCS DNS server are very slow. When setting my client to use an external DNS server the queries are much faster.
The UCS server does not have any forward DNS server set, so for every query it has to ask the DNS-root servers for the domain suffix (ie “.de” or “.com”). Then the authoritative DNS server for this suffix about the domain (ie “univention.de”). And finally the authoritative server to get the IP for the desired hostname. This takes a good amount of time. Especially when requesting hosts for the first time you see a noticeable delay while immediately following request are faster.
When setting to a public DNS the results are send much faster.
Configure public available forward DNS servers. They will cache much more queries and therefore are able to send the replies much fast than going down the way from top to bottom as shown above.
To configure forwarders in UCS please check this article.