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ovs-quantum-agent integration bridge vs physical bridge

Asked by Asif

Hi All,

  In ovs-quantum-agent I see that there are two bridges. One, integration bridge to plugin all VMs VIFs and second physical bridge to communicate with the external world(with l2 learning enabled on both).

Wouldn't it be possible to achieve this with just one bridge say integration bridge? Why use two separate bridges?

thanks
Asif

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Robert Kukura (rkukura) said : 		#1

Hi Asif,

The reason for separate physical bridges for each physical interface is that each physical network has its own independent set of VLAN tag values. The VLAN tags on the integration bridge are locally assigned by the agent. The flow rule that passes data from the integration bridge to a physical bridge replaces the locally assigned VLAN tag used on the integration bridge with the the VLAN tag used on the physical network (or removes it for flat networks). The VLAN tags of data flowing from the physical bridge to the integration bridge are similarly translated by the flow rules. Note that multiple distinct virtual networks can use the same VLAN tag value on different physical networks.

-Bob

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Lingxian Kong (kong) said : 		#2

please read the ovs-quantum-agent code seriously. In my opinion, the main work of ovs-quantum-agent is transformation from local vlan(allocated automatically from 1 to 4094) to physical vlan.

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