S7 communication Problemo

Dear Members,
I have a small problem that i need help on. I have an S7400H system with Etherent CPs and want to establish connection b/w both the CPs and an S73-1-2DP cpu with an Ethernet LEAN CP. The problem is that when i make a connection in my project then the first connection is ok but the connection b/w the second S7400 CP and S7300 CP is having problem. In my proect when i make connection b/w the two stations i get the S7400 Local ID as 0001 A052 ...whereas the other guy gets an ID 0001 A051 as the ID for S7400 CP. Th eproblem is that he dont have option for selecting 0001 A052 like me,,,,,,,wheras i dont have option for 0001 A051 like him,,,.. thus we cannot establish a connection b/w the second S7400 Ethernet CP and the s7300 LEAN CP. I have established communication only b/w the first CP. Thus i can read and write the data but the problem is that if at any time my Master CPU fails and the standby becomes as Master then i will have no connection to the S7300 station and will create serious problem for the plant operatioon... any suggestions will b very much appreciated.

What is really the type of your S7-300 CPU?

The S7-400H end of connection seems right. What type of connection are you using? What block (AG_SEND/RECV?) are you using to communicate and how have you programmed this? Have you programmed both connection is S7-300 PLC?