As an Openstack Administrator for a while, I found the most complicated topic to be understood in openstack project is Networking and how instances ( formerly virtual machines) are communicated with each other and with external world.
Unlike VMWare ESXI, where you can just create vSwitch and attach a VM to it, Openstack Networking is much more complex that that. You need first to define Network type itself(Flat, VLAN, VxLAN, GRE), attach it to the subnet with IPv4 or IPv6 Block, Create a Floating IP address if this network will be connected externally to a provider network and optionally create an internal router to route between different networks and subnets. lots of steps!
Floating ip and neutron router in nutshell
Also Neutron itself doesn’t provide an actual networking to the instances. it just a wrapper to a drivers called “Mechanism Drivers” on which they provide the actual networking(switching, routing and…
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