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Trouble with Layer3 network and neutron.

asked 2020-01-26 16:55:21 -0500

Major-Pickle gravatar image

updated 2020-01-26 16:56:05 -0500

Hi all,

Currently I'm working on a project to setup Openstack Train in a layer 3 routed network. That means the IP the hypervisor (compute node) is assigned is not in the same subnet of where traffic is routed. Further complicating the issue the IP's available to the vms is in another subnet all together.

Each hypervisor has 2 nexthop routes assigned to the subnet. let's say for example the hypervisor has IP 10.2.0.10 in the subnet 10.2.0.0/18. That hypervisor has nexthop routes over the standard interface bridge. eth0 and eth1 which are slaved to br0 each go to separate nexthop routes. We will call these 100.2.5.88 and 100.2.5.89. If we provision an vm it will be assigned an ip from a pool specific to the hypervisor like 10.52.100.0/26. The reason is we have bgp broadcasting the ips as to aid with incoming routing. But we aren't there yet. We can't even get routing off the vm.

No matter what I do with routing inside the vm or on the hypervisor. No matter what settings I pick in neutron I just get nothing. This is with linuxbridge and openvswitch. I've tried letting the routers do it, letting the subnets do it. I've tried neutron segments. I've tried to use the hypervisor as a gateway too. Turning on ipv4 forwarding. But I get nowhere. The network from the vm just doesn't communicate outward.

Simply put letting the hypervisor handle the routing via ipv4 forwarding would be the easiest option. we already have bgp setup too. But at this point I'll take any function. I am using kolla-ansible by the way.

any ideas appreciated. Thank you :)

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answered 2020-01-27 02:40:02 -0500

Hello If you want VM network to reach outside system make sure, VM subnet have correct route table with host gateway ( compute) configured. and route table is correctly configured with all host.

For you case 10.52.100.0/26 should have route table br0 gateway 100.2.5.X should able to reach 10.2.0.X gatway and host physical ip

if all route table are proper, you will able to reach.

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Asked: 2020-01-26 16:55:21 -0500

Seen: 71 times

Last updated: Jan 27