CUCM 7.1.2 does not have the the option to add 3925 gateway as MGCP.
I am sending you the compatibilty matix.
You can confirm which CUCM is supports the 3900 routers by checking the
Cisco 1861 and Cisco 2800, 3800, 2900, 3900, and 3900E Series
Integrated Services Router Interoperability with Cisco Unified
I see that you are running
If you are looking for MGCP support for the 3900 series routers
the requirements are as follows:
1. If you have a 3925 or 3945 router you will need
CallManager 7.1.3 and IOS 15.0.1M
2. If you have a 3925E or 3945E router then will need
CallManager 7.1.5 and IOS 15.1.1T
That information can be found in Table 4 - Cisco Unified Communications
Routers with Cisco Unified Communications Manager Minimum System
Requirements Using MGCP in the link below:
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