Recently a large German telecom provider suffered some technical issues in its network. Several publications traced the issue back to an outage of the company's DNS Servers. So in cases of need please find some information below how to configure your devices to use an alternative DNS Server.The most commonly known alternative to the legacy telco servers is the google DNS server:

• 8.8.8.8 and 8.8.4.4
• beware of privacy issues though

Secondly I came across the Chaos Computer Club which provides some information regarding open and privacy safe DNS Servers:

• CCC information: https://www.ccc.de/censorship/dns-howto/