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Static DHCP Limit?

Discussion in 'Asuswrt-Merlin' started by Allan Marcus, Apr 14, 2019.

  1. Allan Marcus

    Allan Marcus Occasional Visitor

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    Is there a limit to the number of devices that can be registered for static DHCP addresses? The RT-AC68U manual says: "Up to 32 MAC Addresses can be added to the DHCP list for manual assignment"

    Is the limit with ASUS_Merlin also 32?
     
  2. LiFePO4

    LiFePO4 Occasional Visitor

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    I am not sure on the 68U but I think it is 128 (I used to have a 68U and I think that is correct; if you install Merlin it tells you on the DHCP assignment page). It is 128 on the 86U
     
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  3. ColinTaylor

    ColinTaylor Part of the Furniture

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    With the current firmware the number of entries is limited to using 2999 bytes of NVRAM. This means that the exact number of entries will vary depending on the length of the hostname and IP address. But as a rough approximation it will be about 70 entries.
     
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  4. Allan Marcus

    Allan Marcus Occasional Visitor

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    Yep! It's right there on the page:

    Manually Assigned IP around the DHCP list (Max Limit : 128)

    Many thanks.
     
  5. ColinTaylor

    ColinTaylor Part of the Furniture

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    That message is no longer correct since they introduced the NVRAM limits.
     
  6. Allan Marcus

    Allan Marcus Occasional Visitor

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    oh. So how does that relate to DHCP static reservation limits?
     
  7. ColinTaylor

    ColinTaylor Part of the Furniture

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    See my reply in post #3.
     
  8. Allan Marcus

    Allan Marcus Occasional Visitor

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    oops, missed that. thanks.
     
  9. Allan Marcus

    Allan Marcus Occasional Visitor

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    Is there a command to see how much NVRAM is being used for this?

    other than
    nvram show

    which returns this for me
    size: 58873 bytes (6663 left)

    would this be close?
    nvram show | grep dhcp_staticlist | wc
     
  10. ColinTaylor

    ColinTaylor Part of the Furniture

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    Yes that command would work, or this:

    # nvram get dhcp_staticlist | wc -m
     
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  11. RMerlin

    RMerlin Super Moderator

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    The important part is the length of the dhcp_staticlist value, not the space in the nvram storage space. Each nvram entry now has an assigned maximum length, which in many cases I can no longer increase (more specifically with the RT-AC86U and RT-AX88U, which enforces length validation in closed source portions of the firmware).
     
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  12. Allan Marcus

    Allan Marcus Occasional Visitor

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    Ahh, ok. That makes sense.
     
  13. Allan Marcus

    Allan Marcus Occasional Visitor

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    next time I get this error:

    failed to write /var/lib/misc/dnsmasq.leases: No space left on device

    I'll check nvram space and see if that is the issue. Unless you have a better idea. Rebooting the router usually resolves the issue.
     
  14. ColinTaylor

    ColinTaylor Part of the Furniture

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    I was forgetting that some of the "nvram variables" are no longer stored in NVRAM. Is dhcp_staticlist one of those?
     
  15. ColinTaylor

    ColinTaylor Part of the Furniture

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    That has nothing to do with NVRAM or dhcp_staticlist. That error has been discussed in other threads.
     
  16. Allan Marcus

    Allan Marcus Occasional Visitor

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  17. ColinTaylor

    ColinTaylor Part of the Furniture

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    Yes, those and others. Unfortunately the message only indicates a symptom not the cause.
     
  18. RMerlin

    RMerlin Super Moderator

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    Only on HND models, and it's totally transparent - the nvram userspace tool will automatically access the correct location.