Hello,
In your case, the DNS, host name and IP address are going to change... You could use either of the METHOD-
METHOD 1) Complete Reinstall SEPM and restore clients process.
As stated in the Article Below:
How to point clients to a new SEPM after decommissioning or replacing the primary SEPM.
http://www.symantec.com/docs/TECH92556
Here, you Perform the above Disaster Recovery and Logging into the New SEPM, any groups and policies that were previously created will be restored as well as the license file. You will also see your clients listed as Offline. As such you will need to connect your existing clients to the new SEPM. Please refer to the document: Restoring communication to clients with a new Sylink.xml file.
So, the Plan of Action would be -
1) Take the Backup of SEPM 11.x
2) Install the same version of SEPM 11.x and Restore the Database.
3) Restore the Client communication via SylinkReplacer Tool.
http://www.symantec.com/connect/downloads/sylinkreplacer-tool-connecting-sep-clients-sepm
4) Once all the clients, start communicating, start the migration of SEPM 11.x to SEP 12.1 RU1
5) Once all the clients are migrated to SEP 12.1 RU1, start the migration to SEP 12.1 RU1 MP1
METHOD 2) Replication Method - As provided in the Article below:
How to move Symantec Endpoint Protection Manager from one machine to another
http://www.symantec.com/docs/TECH104389
Here are few steps to look at for Migration:
1) How to upgrade the Symantec Endpoint Protection Manager (SEPM) to Version 12.1 RU1
http://www.symantec.com/docs/TECH176260
2) a) Upgrading or migrating to Symantec Endpoint Protection 12.1.1000 (RU1)
http://www.symantec.com/business/support/index?page=content&id=TECH174545
b) Upgrading or migrating to Symantec Endpoint Protection 12.1.1101 (RU1 MP1)
http://www.symantec.com/business/support/index?page=content&id=TECH187753
3) Steps to prepare computers to install Symantec Endpoint Protection 12.1 client
http://www.symantec.com/docs/TECH163112
4) Activating your Symantec Endpoint Protection 12.1 product license
http://www.symantec.com/business/support/index?page=content&id=TECH162623
Also, check the Articles for the Migration on :
Quick Access to Symantec Knowledgebase Articles of Symantec Endpoint Protection 12.1
https://www-secure.symantec.com/connect/articles/quick-access-symantec-knowledgebase-articles-symantec-endpoint-protection-121
SEP 11.x to SEP 12.1 Upgrade process graphical overview
https://www-secure.symantec.com/connect/articles/sep-11x-sep-121-upgrade-process-graphical-overview
WhitePaper for Migration: https://www-secure.symantec.com/connect/downloads/migration-whitepaper-symantec-endpoint-protection-version-121
Hope that helps!!