I am configuring devices for IPT Express (see network diagram atached). Is it better to configure the dhcp pool for the IP Phones on the gateway of the Core switches? And what are the implications. If I have to configure the DHCP on the Core switches, should it be configured on both Core switches? Please advice.
I vote router also. It's also best practice with SRST sites.
In your environment, I would recommend putting it on the router or core layer 3 switch. In large deployments where alot request are being made to issue/renew address it is recommended to send those request to a dedicated server offloading the work to the server instead of the core infrastructure.