Practically we dont use two subnets beteeen the firewall and core switch clusters. It is not a must but as a practice to avoid asymetric routing and complexcity.
Configure FHRRP (HSRP, VRRP or GLBP) on uplinks towards the firewall and then allocate two downlinks ports of the Firewall to a VLAN.
Do a traceroute and check the point where packets drop
Thanks bro
bt FHRPs are not available on the sophos firewall.

Sophos firewall eke OSPF enable karala ne mama 