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<p>Hi Mike,</p>
<p><br>
</p>
<p>With those requirements, I think dual-homing the instances may be the best approach.
</p>
<p><br>
</p>
<p>In my mind, you would have 5 networks:</p>
<p><br>
</p>
<p>A - External Network 1<br>
</p>
<p>B - External Network 2<br>
</p>
<p>C - Tenant Network 1 <br>
</p>
<p>D - Tenant Network 2</p>
<p>E - Shared Tenant Network (No gateway)<br>
</p>
<p><br>
</p>
<p>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:</p>
<p><br>
</p>
<p>Router 1</p>
<p>Router 2</p>
<p><br>
</p>
<p>You would connect them as follows:</p>
<p><br>
</p>
<p>External Network 1 <-> Router 1 <-> Tenant Network 1</p>
<p>External Network 2 <-> Router 2 <-> Tenant Network 2</p>
<p><br>
</p>
<p>The VMs would then connect as follows:</p>
<p><br>
</p>
<p>Tenant Network 1 <-> VM1 <-> Shared Network<br>
</p>
<p>Tenant Network 2 <-> VM2 <-> Shared Network</p>
<p><br>
</p>
<p>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.
</p>
<p><br>
</p>
<p>Hope that helps,</p>
<p>James<br>
</p>
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<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>From:</b> Mike Spreitzer <mspreitz@us.ibm.com><br>
<b>Sent:</b> Wednesday, April 8, 2015 12:28 PM<br>
<b>To:</b> openstack<br>
<b>Subject:</b> [Openstack] [neutron] how to use multiple external networks?</font>
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<div><font face="sans-serif" size="2">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.</font>
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<br>
<font face="sans-serif" size="2">Thanks,<br>
Mike</font> <br>
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