Making DHCP changes
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In the DHCP episode, Don entered some configurations, such as assigning a static then a reserved IP for Wes' laptop. In the dialogue, Wes wanted a different IP and had to release the IP and renew. This may have just been one way to do it, but couldn't the admin who assigned the IP change it at will without the end user releasing the IP and renewing to get a different IP? If so, can you explain briefly how that would be done?
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Richard,
As far as I know, with DHCP it has to be released and renewed. The reason is the duration of the original lease. By default, in Microsoft's DHCP server, it has an 8 day lease, this would be true of the Dynamic and the Reserved Addresses. The difference is that with a dynamically assigned address, Wes could have received a different IP address at the end of the lease. With the reservation, at the end of the lease, Wes would have received the same address again because it's mapped to the MAC address.
Either way, Wes machine would not have released the address until the end the lease. The admin could change the reservation and provide a different address but Wes would have not received the address until he released it or rebooted the computer. Rebooting the computer could cause it without having the user issue the
ipconfig /release
andipconfig /renew
Anyone, know any differently, please chime in!
Cordially,
Ronnie Wong
Host, ITProTV -
I'm not 100% sure but I think just the renewal is necessary. If you have a DHCP address with lease time left and reboot when the DHCP server is unavailable, you will keep using the same address. If you do an ipconfig /release and /renew while the dhcp server is unavailable, you will get a MS 169 bogus address. If you reboot while the DHCP server is available while you have a lease with time left but the admin has set new information (like a reservation) then the computer will take the new lease.
When I am doing server migrations I will update DHCP scopes for things like new DNS servers and if users have difficulties I will often tell them to reboot. It's easier then walking them through the release/flushDNS/renew process.
Phil