I asked for similar information earlier this year.  Below is a response that
I received from this list.  We decided against using ADSM for backups over
the firewall.  One of our main concerns was bandwidth.

Debbie,

I have implemented a solution to backup ADSM Solaris clients residing
outside of a firewall to an ADSM/6000 server residing behind the firewall.
 The following two ports must be enabled for directional traffic to the
specific addresses outside of the firewall:

1500 -  inbound to the ADSM server
1501 -  outbound to the ADSM client

If you want to use HSM you will need to enable an additional port.  I
suggest that you set the SCHEDMODE to  POLLING, we were unable to get the
client to backup consistently using a SCHEDMODE of PROMPTED.  I hope this
was helpful.

DanC
=============================================
Daniel G. Crouse
IBM Certified Specialist - ADSM