[Openstack] [neutron] how to use multiple external networks?

Mike Spreitzer mspreitz at us.ibm.com
Thu Apr 9 01:35:34 UTC 2015


Oops, my original email did not contain all of the constraints.  Each 
compute instance gets only one network interface, only one IP address. 
Does Juno Neutron have a way to solve this problem?

Thanks,
Mike



From:   James Denton <james.denton at rackspace.com>
To:     Mike Spreitzer/Watson/IBM at IBMUS, openstack 
<openstack at lists.openstack.org>
Date:   04/08/2015 07:04 PM
Subject:        Re: [Openstack] [neutron] how to use multiple external 
networks?



Hi Mike,

With those requirements, I think dual-homing the instances may be the best 
approach. 

In my mind, you would have 5 networks:

A - External Network 1
B - External Network 2
C - Tenant Network 1 
D - Tenant Network 2
E - Shared Tenant Network (No gateway)

Because routers can only connect to one external network at a time, and a 
tenant network can only be connected to one router at a time, you would 
need two routers:

Router 1
Router 2

You would connect them as follows:

External Network 1 <-> Router 1 <-> Tenant Network 1
External Network 2 <-> Router 2 <-> Tenant Network 2

The VMs would then connect as follows:

Tenant Network 1 <-> VM1 <-> Shared Network
Tenant Network 2 <-> VM2 <-> Shared Network

With no gateway set on the shared network, you won't have to worry about 
multiple default routes, nor do you need to worry about terminating that 
network off a router. It's simply isolated. 

Hope that helps,
James

From: Mike Spreitzer <mspreitz at us.ibm.com>
Sent: Wednesday, April 8, 2015 12:28 PM
To: openstack
Subject: [Openstack] [neutron] how to use multiple external networks? 
 
Supposing there are two external provider networks, and a tenant wants (a) 
some of his Compute Instances to have floating IP addresses on one of 
those external networks, (b) some other of his Compute Instances to have 
floating IP addresses on the other external network, and (c) all of his 
Compute Instances to be able to talk to each other using only tenant 
private networking, what arrangement of tenant networks and routers would 
accomplish this?  In Juno, if it matters. 

Thanks,
Mike 

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