neutron

why dhcp_lease_time default value is 120s?

Asked by Matt Mao

In dhcp agent the default value of dhcp_lease_time is 120, this means the lease time is 120s, why we use such a short time?
why do not we use 24 hours or some other longer time ? Thanks.

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Aaron Rosen
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Best Aaron Rosen (arosen) said : 		#1

The lease time was low because previously the neutron-dhcp-agent didn't have a way to release the lease until it timed out. In the havana release the lease time is set to 24 hours though and the ip address can be reclaimed after a port is deleted.

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Matt Mao (maoliping455) said : 		#2

Thanks Aaron Rosen, that solved my question.

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yong sheng gong (gongysh) said : 		#3

The long time will have a side effect:
If I update the port's IP via API, and the VM will not be updated until the long timeout.

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andrew yongjoon kong (sstrato-kong) said : 		#4

@yong sheng

i agreed.

and it can be affected to live migrated vm ( like some one using multiple gateway and zones, it will take time to notice the gateway ip is changed by dhcp timeout)