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 windsurfer on Tuesday July 12, 2011 @03:36PM (#2756163)

How is this the DHCP server's fault? DHCP is designed to reassign unused leases to new clients if the subnet is all leased out.

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Re:Rapid DHCP: Or, how do Macs get on the network so fast? by tomlogic on Tuesday July 12, 2011 @03:56PM (#2756250)

How can a lease be "unused" if it hasn't expired and the client that requested it never released it? Are you saying that the DHCP server pings (ICMP or ARP) each address and re-leases the ones that don't get a response?

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Re:Rapid DHCP: Or, how do Macs get on the network so fast? by windsurfer on Tuesday July 12, 2011 @04:09PM (#2756310)

Well actually the result of "running out" of addresses is undefined and up to the individual hardware manufacturer, so theoretically they could do whatever they want. A high-traffic WAP might want to simply boot the oldest lease if they can't assign more than a certain number of addresses.

Keep in mind if aa client wants an IP, it is supposed to do DHCP discovery every time it connects to the network, even if it's lease isn't up. See http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Prot...

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Re:Rapid DHCP: Or, how do Macs get on the network so fast? by brk on Tuesday July 12, 2011 @04:06PM (#2756299)

Are you saying that the DHCP server pings (ICMP or ARP) each address and re-leases the ones that don't get a response?

The DHCP will ping an address before leasing it, and if it gets a response then it will not lease that address.

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Re:Rapid DHCP: Or, how do Macs get on the network so fast? by m_eiman on Wednesday July 13, 2011 @05:33AM (#2758379)

I don't think this is true at our office (running a Cisco DHCP server). We get conflicts when putting a device with a static IP in the dhcp range, and I'm almost sure that they respond to ping.

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