Neutron network information

asked 2019-03-06 04:07:27 -0600

dhanesh gravatar image

updated 2019-03-11 09:10:04 -0600


Please help me understand openstack networking.

My understanding: -

We have three type of virtual network in neutron. 1.flat 2. Vlan 3. Vxlan/gre

Based on the above type wat are the different ways we can create private and public network. Why are we using flat network? Suppose I am using flat network. will I be able to create multiple private networks for my project? Will I be able to create floating network and allocate to private network of instance?

Private network only for internal ip of instance. Public network will create public subnet and use as floating ip. We can either assign public up network from network provider or can use ip address which has internet.

Please give example for each case.

Regards, Dhan.

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answered 2019-03-09 18:25:12 -0600

chalans gravatar image

Flat or Vlan depending on your physical configuration. Usually we have multiple vlan on a trunk inside your external interfaces so the ml2 provider was configuration on Vlan mode. And yes, that for public network / provider Network for FIP but you can assign directly an public IP on your Instance.

Indeed , Vxlan are for private IP on instance.

Not sure if i answered on your questions ;)



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answered 2019-03-11 09:15:50 -0600

updated 2019-03-11 09:20:34 -0600

You need a flat network if you want to map an external network in your cloud to a physical network in your datacenter. The external network will be of type flat.

Your users may not have the need to create their own networks. All they need are instances connected to the internet or intranet. One or more flat networks are fine in this case, and instances connect directly to them. Flat networks don’t support floating IPs, routers and tenant networks.

If the users in your cloud require the ability to set up their own network structures consisting of several tiers and routers, their virtual networks must be separated from each other, although they are typically implemented on a single physical network. Neutron offers VLAN, VXLAN and GRE as separation mechanisms. VLAN is limited, since not more than 4096 VLANs are possible on a physical network, and VLANs can’t cross networks. GRE removes these limits but since it consists of a separate IP type, routers may not like it. VXLAN uses UDP, which is normally not blocked by routers.

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Thanks for sharing the input.

Please clarify below.

Difference between Flat network, provider network, self service network. Please add if i messed any network in Openstack.

dhanesh gravatar imagedhanesh ( 2019-04-25 02:43:39 -0600 )edit


self-service is another term for tenant network. It's a network a user can create and manage. This is in contrast to provider networks, which only an administrator can create and manage.

Bernd Bausch gravatar imageBernd Bausch ( 2019-04-25 22:29:44 -0600 )edit

Another good article clarifying the terms tenant and provider:

Bernd Bausch gravatar imageBernd Bausch ( 2019-04-25 22:31:44 -0600 )edit

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Asked: 2019-03-06 04:07:27 -0600

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Last updated: Mar 11 '19