OpenStack Networking L2 and L3 Agent

1)
A bite of virtual linux networking
http://fosskb.wordpress.com/2014/06/25/a-bite-of-virtual-linux-networking/

2)L2 Agent
neutron-openvswitch-agent (provide l2 connectivity to the instances)

a)
L2 connectivity in OpenStack using OpenvSwitch mechanism driver
http://fosskb.wordpress.com/2014/06/19/l2-connectivity-in-openstack-using-openvswitch-mechanism-driver/ <== IMP

* neutron-openvswitch-agent to provide l2 connectivity to the instances running on compute nodes.
* The neutron-openvswitch-agent emulate as though the virtual machines on multiple compute hosts are on the same L2 segment.

b)
VLANs at layer 2 are equivalent to Subnets at layer 3. Use VLAN to group VMs at Layer 2 and Use subnet to group VMs at Layer 3.

3)
L3 Agent
neutron-l3-agent (provide l3 connectivity)

a)
L3 connectivity using neutron-l3-agent
http://fosskb.wordpress.com/2014/09/15/l3-connectivity-using-neutron-l3-agent/

b)
http://docs.openstack.org/admin-guide-cloud/content/install_neutron-l3.html

The OpenStack Networking Service has a widely used API extension to allow administrators and tenants to create routers to interconnect L2 networks, and floating IPs to make ports on private networks publicly accessible.

Many plug-ins rely on the L3 service agent to implement the L3 functionality. However, the following plug-ins already have built-in L3 capabilities:
* Big Switch/Floodlight plug-in
* IBM SDN-VE plug-in
* NSX plug-in
* PLUMgrid plug-in

*** Do not configure or use "neutron-l3-agent" if you use one of these plug-ins.

* To install the L3 agent "neutron-l3-agent" for all other plug-ins like OpenVswitch, linuxbridge, follow
http://docs.openstack.org/admin-guide-cloud/content/install_neutron-l3.html

c)
http://docs.openstack.org/developer/neutron/devref/layer3.html