Further question,

A system has an internal MIPU and one with a public address.
Phones registering on the internal address seem to have to have the PDN equipment number set to the one of the internal MIPU and then when they are outside the network, the primary ipu address(internal) fails and but the secondary (public on the 2nd mipu) using the public address of the second MIPU come back with a resource full error.

If I change the pdn equipment number to that of the 2nd mipu card, then the phone registers.

Is there no way configure the phone so it can connect via the internal mipu when it is in the office and the external mipu when it is outside without having to constantly change the settings in emanager?

Using the external address when in the office seems like unnecessary hops and potential for poorer call quality.