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Old 5th April 2020
cal70 cal70 is offline
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Default OpenBSD DHCPD help

I'm new to the board, hoping that I will be able to draw on the knowledge of this group to help grow my skills. I am running OpenBSD at home running PF, Unbound, NSD, and others.

Right now, my DHCP server is set up for lease time of 1 wk. BUT I have several clients that are flooding the daemon log every few min. polling for DHCP services. I have looked in the dhcpd.lease file and it's pepperd with these clients.

SO my question is -> Is this normal? If not, how do you clear the lease or dhcp database (safely) to start fresh.

I have snippets from logs if that would help...
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Old 5th April 2020
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jggimi jggimi is offline
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Hello, and welcome!

To my understanding, you can set the server to offer long lease times, but a client can ask for and receive as short a lease as it wants. It will only be given your server's default-lease-time if it does not request a specific lease time.
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Old 5th April 2020
cal70 cal70 is offline
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Thank you... appreciate the help. That seems to make sense too. I will treat that as normal, now that I am seeing all the traffic on the network, hard to tell what is good (normal) or bad / misconfiguration.

Cheers!!
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Old 6th April 2020
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According to RFC 2131, which superseded RFC 1541, one of the revisions in 2131 was to remove a minimum-lease-time restriction.

As the clocks in the client and server are not expected to be kept in sync, the client may use a shorter lease time than the negotiated time. Further, while I don't see it articulated in the RFC, common client behavior is to request a renewal at 50% of the negotiated lease time.

Last edited by jggimi; 6th April 2020 at 01:09 PM. Reason: clarity
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