In my topology I have four devices (Gateway, router1, router2, end-node). Gateway, router1, router2 have 2 interfaces each. On Gateway one interface is connected to NAT and other interface is connected to router1. On router1 one interface is connected to Gateway and other interface is connected to router2. On router2 one interface is connected to router1 and one interface is connected to end-node. Gateway is configured and DHCP Server, router1 and router2 are configured as Relay Agent. But router1 OS is Windows Server 2019 and Router2 OS is Ubuntu 22.04 LTS. End-Node is configured as DHCP Client. I have configured server, relay agent but I am struggling with firewall. Allow only traffic from Local DHCP Server, DHCP Relay, DHCP Client.