DHCP lease time query

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This topic contains 9 replies, has 5 voices, and was last updated by Blood Blood 1 year, 4 months ago.

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  • Author
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  • Blood
    Blood
    Moderator
    #167140

    Hi, Folks

    We use DHCP for some of our clients. DHCP uses a single scope and has the lease time set to 8hrs. I was looking at my machine which has an address assigned via a DHCP reservation and ipconfig /all shows the lease time as 2 days and 8hrs.

    Has anyone encountered this before or know why the configuration has been over-ridden, please?


    biggles77
    Spectator
    #214209

    Blood, can you attach the image again because I get an Invalid page URL. I have seen this a day or so ago so I begin to wonder…… Let’s see if I can do it.


    biggles77
    Spectator
    #214210

    Ok, something is broken I think. If others can see the attached images or cannot see the attached images in both the above post, please advise accordingly below. I want to make sure that it isn’t my machine playing silly buggers.

    Thanks.


    Ossian
    Moderator
    #191771

    Not you, Chris – its a feature :twisted:

    Blood
    Blood
    Moderator
    #337308

    Aha – I thought my machine was playing up. I initially tried uploading an image but nothing was displayed. Tried it as an attachment next, but that has obviously failed as well.

    Anyway, the image simply showed the DHCP options box with the lease time set to 8hrs. It’s running on W2008 Standard. Next to it was the output from ipconfig /all from my W7 client that shows 2 days and 8 hrs:

    Ethernet adapter Local Area Connection 10:

    Connection-specific DNS Suffix . : mydomain.local
    Description . . . . . . . . . . . : Intel(R) PRO/1000 GT Desktop Adapter
    Physical Address. . . . . . . . . : 90-E2-BA-E1-88-D9
    DHCP Enabled. . . . . . . . . . . : Yes
    Autoconfiguration Enabled . . . . : Yes
    Link-local IPv6 Address . . . . . : fe80::7dd6:ca76:6081:78bd%23(Preferred)
    IPv4 Address. . . . . . . . . . . : 192.168.0.147(Preferred)
    Subnet Mask . . . . . . . . . . . : 255.255.255.0
    Lease Obtained. . . . . . . . . . : 09 August 2017 08:52:45
    Lease Expires . . . . . . . . . . : 11 August 2017 16:52:51

    Default Gateway . . . . . . . . . : 192.168.0.95
    DHCP Server . . . . . . . . . . . : 192.168.0.10
    DNS Servers . . . . . . . . . . . : 192.168.0.17
    192.168.0.10
    Primary WINS Server . . . . . . . : 192.168.0.16
    NetBIOS over Tcpip. . . . . . . . : Enabled


    joeqwerty
    Moderator
    #304606

    Some companies will set a short lease time if they have a lot of wireless clients and/or if they have a lot of stale DNS records. I’ve seen an 8 hour lease time at a few companies.

    Blood
    Blood
    Moderator
    #337309
    joeqwerty;n512297 wrote:
    Some companies will set a short lease time if they have a lot of wireless clients and/or if they have a lot of stale DNS records. I’ve seen an 8 hour lease time at a few companies.

    Thanks, Joe

    I want the lease time to be 8hrs. There are a small number of domain-joined clients on the network (35), and probably about 15-20 wireless devices (mostly phones) so it’s not being bombarded with DHCP requests. I set it to this time because I found my self cleaning up stale records from DNS and DHCP. Since setting the shorter time I’ve not seen these re-occur.


    JeremyW
    Moderator
    #271551

    There’s nothing wrong here. What is happening is that computers will renew their leases which restarts the clock. But the lease is still the original that was obtained.

    Run an ipconfig /renew and then check the times again. You should see the lease obtained at the same time but the expires should be updated.

    Also note that DHCP clients will attempt to renew the lease when half the lifetime has passed.

    Blood
    Blood
    Moderator
    #337310

    Aha! Thank you very much, Jeremy.

    I just ran ipconfig /all and the lease values are:

    Lease Obtained. . . . . . . . . . : 09 August 2017 08:52:45
    Lease Expires . . . . . . . . . . : 14 August 2017 16:52:56

    I knew about the DHCP default renewal times but just assumed that the lease obtained value would be updated – I had not realised that as it’s not a new lease per se, the original value would remain.

    Cheers :)


    JeremyW
    Moderator
    #271553

    Glad to help. 8)

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