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Multiple l3-agents on different hosts for same external network

asked 2014-09-26 09:23:30 -0500

envy gravatar image


I'm currently building a three host OpenStack setup at my university. Currently one host is handling all controller stuff while also being a compute node and the network node with the l3-agent. Now I wondered if it is possible to add a second (and third) l3-agent on the two other hosts and use them for the same external network.

The gain would be, that VMs on host 2 don't have to go to host 1 to get to the internet, but can go directly via host 2.

Is this possible? Again, I don't want multiple external networks, it's the same network for all l3-agents.

Thanks for your help.

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answered 2014-09-26 12:39:14 -0500

larsks gravatar image

It is not currently possible to run multiple L3 agents for a given network.

You may want to read up on the Neutron Distributed Virtual Router (DVR) effort, which aims to (a) provide Neutron with better availability and (b) to reduce the use of a single L2 router for communication between servers on the same network.

As far as I can tell, this effort does not address your specific use case -- specifcally, I do not believe it supports more than a single active L3 agent for a given external network (but it does provide for failover -- including connection tracking information -- for L3 routers).

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Hi, thanks for your response. In my lab environment I setup multiple L3 agents while only having one external network and noticed that everything was still working fine but the virtual routers were distributed over the L3 agents. I assume this is what you meant with your last sentence?

envy gravatar imageenvy ( 2014-09-28 09:01:16 -0500 )edit

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Asked: 2014-09-26 09:23:30 -0500

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Last updated: Sep 26 '14