you have to setup mirror
<mirror>
<id>nexus</id>
<mirrorOf>*</mirrorOf>
<url>http://internal/nexus/content/repositories/thirdparty</url>
</mirror>
<mirror>
<id>google</id>
<mirrorOf>google</mirrorOf>
<url>http://google-maven-repository.googlecode.com/svn/repository</url>
</mirror>
then add internal & external repo
<profile>
<id>nexus</id>
<repositories>
<repository>
<id>central</id>
<name>central</name>
<url>http://internal/nexus/content/repositories/thirdparty</url>
</repository>
<repository>
<id>google</id>
<name>google</name>
<url>http://google-maven-repository.googlecode.com/svn/repository</url>
</repository>
</repositories>
</profile>