Openstack: How to give the management network Internet?

Question

I'm an OpenStack beginner and want to install it with openstack-ansible following the official guide.

I have 4 machines each have 2 NICs. One of the machines is the typical "deployment host" to install openstack to the 3 other hosts. The first NIC is for external Network / Internet for exposing VMs and the second NIC is connected with a switch for the internal management network (br-mgmnt <-> NIC2 <-> switch <-> other machine's NIC2).

The problem is that the switch has no do NAT and has no external network access, so internal services in the management network have no Internet. But Internet for the management network is needed as documented in: https://docs.openstack.org/newton/install-guide-ubuntu/environment-networking.html

Management on 10.0.0.0/24 with gateway 10.0.0.1 This network requires a gateway to provide Internet access to all nodes for administrative purposes such as package installation, security updates, DNS, and NTP.

1. How can I work around this and provide Internet to the management network?
2. Can I use iptables to route all traffic that is not an internal destination from the management network to use the external networking NIC instead of using the switch?
3. Or should I install a NAT router / gateway on one of the host machines to give the switch Internet to the management network? (switch <- internal -> NIC2 <-> NAT <- external -> NIC1)
4. Is here even another network topology I should consider?

Thanks for the help!

Answer 1

You should strip 'openstack' from description of this problem. It's usual complication on 'private network'. You want to have an isolated network, but you need to have some external resources available to you.

Normally you should have your private network having some limited internet access (fe NAT or proxy server).

Some providers (fe servers.com) provides some nice things in their private network (dns, ntp, package mirrors).

Alternatively you can use two internet networks and assign on of them to be 'management'.