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DHCP Leases

By jbellusci ·
When a DHCP IP address lease expires does the workstation get that same IP address right back?

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DHCP Leases

by Some Guy in Seattle In reply to DHCP Leases

The DHCP protocol specifies that halfway through the lease period a client will request an extension/reassignment of the same IP it has been using (for instance, for a 10 day lease the client will begin requesting the extension after 5 days have elapsed). If the DHCP server replies with an affirmative extension the client then begins the count all over again, and the DHCP server updates its lease table.

If there is no response from the DHCP server (broken, reassigned, down, hacked, whatever) the client will continue to try to reacquire the same lease from the same DHCP server at closer and closer intervals until the lease expires. At this point the client then sends out another BOOTP request for any listening DHCP server in an attemptto gain another IP.

Typically, a DHCP server will match a client's MAC address to an IP in it's table, and most of the time will give that same address even if the client machine is rebooted or the IP is /released /renewed. The IP will generallyonly change if the scope is close maxed out and IPs are truly dynamic with clients competing for a limited pool.

Hope that helps,

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by jbellusci In reply to DHCP Leases

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by SteveD In reply to DHCP Leases

Normally, yes. But it's not reserved unless you've created a specific reservation on the server. If a workstation is disconnected or shut down when its lease expires, and a new workstation comes on line while the first one is still off line, then the new one could get the old one's IP address.

I hope this helps.

Steve Diamond

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by SteveD In reply to DHCP Leases

I should have written one more sentence. Then, when the first workstation comes back on line, it will get a different IP address because the new workstation already has its old one. (This is probably quite obvious, but I wanted to be complete!) - SD

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by jbellusci In reply to DHCP Leases

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by jbellusci In reply to DHCP Leases

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