MSHOST or ASHOST?

Hi everyone,

Our SAP production system runs on two application servers serverA and serverB, and they both are added in the logon group SVRGRP.

Now the sap system has a fully qualified domain name - sapprdecc.domain.com and i am able to connect using the string:

ASHOST=sapprdecc.domain.com SYSNR=00 TRACE=0

I understand that we can connect to the msgserver as well. I have tried the following connection strings but none of them work:

MSHOST=sapprdecc.domain.com R3NAME=XX1 GROUP=SVRGRP

MSHOST=xxx.xxx.xxx.xxx R3NAME=XX1 GROUP=SVRGRP

So, i am thinking of going with the ASHOST string(since this works). I have two questions:

1. Can someone please let me know whether i should go for the MSHOST string for my scenario or ASHOST string is enough?
2. Why did my MSHOST string fail, what i am doing wrong?

PS: I am able to open the GUI with the command SAPGUI xxx.xxx.xxx.xxx 00 (so the ipaddress i am using is correct)