I have been asked to put in place a new SCCM Central Site server over 2 existing SCCM environment is different domains (with a full trust between). Both existing environment have similar heirarchy with a Primary and 50+ secondary sites. First I guess I should ask is it possible and then how would I connect them without impacting the existing environments?

It's possible. As long as you do not share the same boundaries you shouldn't have any problems.Kent Agerlund | My blogs: http://blog.coretech.dk/author/kea/ and http://scug.dk/ | Twitter @Agerlund | Linkedin: /kentagerlund

So build the new Central server and point the 2 existing primary servers to it as a parent? Niether of the existing environments cross site boundries? Or are talking IP subnets?