Networking :: apt-get

hi all
i need your help. when i type apt-get update i have this message:
Hit http://ftp2.de.debian.org unstable/non-US/contrib Packages
Hit http://ftp2.de.debian.org unstable/non-US/contrib Release
Hit http://ftp2.de.debian.org unstable/non-US/non-free Packages
Err ftp://ftp.gwdg.de woody/main Packages
 Temporary failure resolving 'ftp.gwdg.de'
Hit http://ftp2.de.debian.org unstable/non-US/non-free Release
Hit http://ftp2.de.debian.org unstable/main Sources
Hit http://ftp2.de.debian.org unstable/main Release
Hit http://ftp2.de.debian.org unstable/contrib Sources
Hit http://ftp2.de.debian.org unstable/contrib Release
Hit http://ftp2.de.debian.org unstable/non-free Sources
Hit http://ftp2.de.debian.org unstable/non-free Release
Hit http://ftp2.de.debian.org unstable/non-US/main Sources
Hit http://ftp2.de.debian.org unstable/non-US/main Release
Hit http://ftp2.de.debian.org unstable/non-US/contrib Sources
Hit http://ftp2.de.debian.org unstable/non-US/contrib Release
Hit http://ftp2.de.debian.org unstable/non-US/non-free Sources
75% [Waiting for headers] [Connecting to ftp.gwdg.de
i can't connect at ftp.gwdg.de
thanks for your help

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