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When Ports get IP via DHCP service, does it also generate a Neutron Port update call to Neutron service?

asked 2017-02-22 13:35:53 -0500

When DHCP assigns new IP to a port, does Neutron service get a port update call with the fixed ips? I still can't find any documentation that explicitly says it does or it doesn't. Can somebody point me towards a documentation that helps me clarify this point?

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answered 2017-02-22 21:09:47 -0500

updated 2017-02-22 21:11:42 -0500

Ports don't get IPs from DHCP. It's the opposite: Neutron assigns IPs to ports upon creation, and the DHCP server sends that IP to the instance when the instance issues a DHCP request.

When an instance is launched, however, the port is bound to the virtual machine host where the instance is scheduled. This means the required physical plumbing is set up, depending on the core plugin and (if the core plugin is ML2) mechanism driver(s) used. Nova-compute does that via a Neutron port update API, which you can see in the log files if debug logging is enabled.

There is a nice summit presentation on port binding. Another more advanced presentation on hierarchical port binding is for people with a stronger networking background than me.

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Asked: 2017-02-22 13:35:53 -0500

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Last updated: Feb 22 '17