IBM p5 590 System Handbook page 245

Remote Support Facility
Enables the HMC to call out to IBM for problem reporting as well as enabling
remote access to your managed systems (if enabled by a client).
Service Focal Point
Collects system management issues in one central point for all your
partitions.
You can select the connectivity method you want to use when communicating
electronically with IBM. There are three options available to you:
Dial-up from the local HMC
This option will use the IBM supplied modem with the HMC to dial in to the
IBM support network. You may choose this option if your HMC doesn't have a
high speed Internet connection through an open network or has only been
configured in a private network.
Virtual private network (VPN) through the Internet
This option will use a high speed Internet connection to connect to the IBM
support network. This is the fastest option available on the HMC, however
your company may restrict this type of connection.
The minimum requirements for call home service connection through a
firewall requires port 500 (TCP and UDP) and port 4500 (UDP). If the HMC is
located behind a NAT router, end points 207.25.252.196 and 129.42.160.16
should be specified.
Connecting through other systems or partitions over the intranet
This option sends information through another system in your network that
can connect to IBM. The pass-through system could be another HMC (only
supported pass-through servers are i5/OS based systems).
Next is the configuration for call home with the modem (Figure 8-23).
Chapter 8. Hardware Management Console overview
223