I have two networks, one internal to openstack " internal_network" 10.10.10.0/24 and an external Network "public" which is connected to an external network 192.168.100.0/24 in order to connect instances to "public" network, I created a router of which the gateway is public network, and also connected to internal_network, and used floating ip to access vm instances from the external network (public), but the problem I have encountered now is that I want to expose the and Ip from the external network inside the vm instance , but when I try to directly attach an interface from the external network to the instance, I don't get and Ip address inside the instance, and even if I assign it manually it still doesn't work, I can't use enable DHCP with public network because it already has its own external dhcp server. How can I solve this problem?