Static DHCP Limit?

[Allan Marcus]

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?

 

[LiFePO4]

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?

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

 

[ColinTaylor]

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.

 

[Allan Marcus]

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

Yep! It's right there on the page:

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

Many thanks.

 

[ColinTaylor]

Yep! It's right there on the page:

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

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

 

[Allan Marcus]

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

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

 

[ColinTaylor]

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

See my reply in post #3.

 

[Allan Marcus]

See my reply in post #3.

oops, missed that. thanks.

 

[Allan Marcus]

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

 

[ColinTaylor]

Yes that command would work, or this:

# nvram get dhcp_staticlist | wc -m

 

[RMerlin]

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).

 

[Allan Marcus]

Ahh, ok. That makes sense.

 

[Allan Marcus]

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.

 

[ColinTaylor]

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).

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

 

[ColinTaylor]

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.

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

 

[Allan Marcus]

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

you talking about this thread?

https://www.snbforums.com/threads/f...pace-left-on-device-retry-in-60s.28247/page-2

Or this one?
https://www.snbforums.com/threads/d...q-leases-no-space-left-on-device.49612/page-2

There was no resolution to the error there :-(

 

[ColinTaylor]

you talking about this thread?..

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

 

[RMerlin]

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

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