When happens when a OVN network and its subnet get created

1. A logical switch will be created, using command "ovn-nbctl show" to verify. 
2. A number of ports will be automatically added, these ports are for DHCP agent instances. They normally should occupy first few IPs in the subnet, for example, if the subnet is 172.16.31.0/24, then most likely 172.16.31.2 and 172.16.31.3 will be used for two DHCP agents if neutron is configured to have two dhcp agents per network. 172.16.31.1 will be most likely reserved for gateway if default is used. The neutron config parameter to control how many dhcp agents should be for a network is "dhcp_agents_per_network"
3. A namespace will be created on all compute nodes, the server runs ovn-northd actually will not have the namespace unless that node is also a compute node.
4. On the compute node where dhcp agent runs, there should be a new dnsmasq instance which allocate the IPs for the subnet. 
5. There should be one Port_Binding entry on each chassis for the new network. Use "ovn-sbctl show" to verify, this is probably due to the dhcp agent port.
6. Port_Binding table by using "ovsdb-client dump tcp:127.0.0.1:6642" (where the southbound database is located) should show that each port will use different tunnel key.
7. br-int bridge should have a port/interface for the dhcp server. Use "ovs-vsctl show" command to verify, here is an example:

    Bridge br-int
        fail_mode: secure
        Port "tap97ef22d4-c7"
            Interface "tap97ef22d4-c7"
                type: internal

8. Anything more?