I am planning for the Exchange 2010-2013 migration, the migration is from one Geo-location to the other. In the current setup, I have 2 CAS and 2 MBX servers with one CAS pointing to the public IP mail.domain.com and autodiscover.domain.com for the external users' access.
I will have the same setup in the new site that I am building the Exchange 2013 servers. Moving the users' mailbox from 2010 to 2013 is not going to happen overnight, so I would like to seek some advise on how do I ensure coexistence for the users existing in both Exchange 2010 and 2013 environment during the migration process. When it comes to configuring the 2013 CAS, can I still have my external URLs same as the 2010 CAS?
Any suggestions and sharing the best practices are much appreciated, thanks!