Rapid DHCP: Or, how do Macs get on the network so fast?

Re:Rapid DHCP: Or, how do Macs get on the network so fast? by deskamess on Tuesday July 12, 2011 @07:05PM (#2757020)

I think your description is correct.

The problem is the impact of the false "ip conflict" that is caused by this optimization. A device that detects an ip conflict should not have to guess whether it is an ip conflict caused by an optimization on another device. As pointed out in other comments an ip conflict can cause other systems to drop existing connections.

No one likes ip conflict notifications, or to have their connections dropped. Play nice. That's all.

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Re:Rapid DHCP: Or, how do Macs get on the network so fast? by rlpb on Tuesday July 12, 2011 @08:00PM (#2757170)

The problem is that the DHCP server re-issued a valid lease to a second computer. Surely this is an issue with the DHCP server not playing nice, rather than Apple?

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Re:Rapid DHCP: Or, how do Macs get on the network so fast? by jarek on Tuesday July 12, 2011 @08:20PM (#2757230)

Do you feel there is a better, more tolerant, and less error prone course of action the DHCP server could take if it runs out of leases?

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Re:Rapid DHCP: Or, how do Macs get on the network so fast? by rlpb on Tuesday July 12, 2011 @10:09PM (#2757499)

If we are able to modify the DHCP server to do something sensible, why not modify default router settings to issue /16 addresses instead of /24? Or even 10/8? There's plenty of RFC1918 space to not run out.

NAT state tables won't have to stretch that far as they can time out unused connections just like they do already.

Would there be any unintended side-effects with doing this?

If you don't like the NAT, go ahead and issue IPv6 :-)

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Re:Rapid DHCP: Or, how do Macs get on the network so fast? by hristov on Tuesday July 12, 2011 @11:53PM (#2757709)

Not really. The DHCP server may have many valid reasons for reissuing a technically valid lease, such as it being restarted and losing its table of valid leases. As I pointed out in a response above, the DHCP protocol makes it clear that devices should re-verify their addresses after waking up.

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Re:Rapid DHCP: Or, how do Macs get on the network so fast? by tzs on Tuesday July 12, 2011 @10:14PM (#2757512)

This optimization does not cause IP address conflicts. If a DHCP server is not correctly keeping track of lease times and ensuring that addresses already assigned are not reused while the client still has a valid lease, you can get IP conflicts regardless of whether or not their are any Apple devices on the network.

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