I need to configure site to site VPN. One of the peer has dynamic IP. The hostname of the peer is qpmmoroc.dyndns.org. I am able to ping this from the firewall but how do i configure the perr using hostname
Make sure you have NAT exemption configured between the 2 subnets.
Unfortunately not a supported configuration. You would need to configure dynamic to static LAN-to-LAN tunnel as per the following sample configuration:
VPN tunnel can only be initiated from the dynamic end.