How to use Openswan as a branch-office device when talking to a Nortel Contivity is here: http://www.freeswan.ca/docs/Contivity/
Note: you currently can't use Openswan as a client (eg: XAUTH Username/Password/GroupID). Xelerance is interested in adding this functionality, however it would have to be sponsored/funded by someone, as it is a non-trivial piece of work.
