Upgrade to EHP7

Hi

I am upgrading my ECC -EHP5 box to EHP7

Currently they are connected with CRM 7.0 and Portal 7.02 systems.

My concern is that if i upgrade my ECC box from EHP5 to EHP7, would i require to upgrade my CRM and Portal boxes as well to NW 7.31 stack??

Thanks

Tushar