What is messing with my dhcpd.conf settings?

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What is messing with my dhcpd.conf settings?

Postby rgmhtt » Sun Jan 11, 2009 8:14 pm

OK. So I set up /etc/dhcpd.conf the way it needs to be (for my 1st approximation).

I reboot, and it is back to the Amahi default that has the wrong netmask, wrong subnet address, wrong lease addresses....

So I need to control what the boot process is doing so I can work on getting a sophisticated dhcpd.conf working?

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Re: What is messing with my dhcpd.conf settings?

Postby cpg » Sun Jan 11, 2009 11:17 pm

wow, you're swimming way under water :)

it's all driven by database settings and designed for stability (hence the re-syncing of state on each reboot, to avoid issues with transient errors). this is after a lot of experience to make things more stable.

honestly, though, i am not sure if amahi is for you at this stage, i'm sorry to say :(

this is not to discourage you at all. but the amahi system is designed for a simpler, less complex network structure than what you seem to have. and it's meant to be managed via the web interface.

now - let met get to the point.

the settings are in the mysql database and they are propagated through the system any time settings are changed.
(i should say that that propagation is sub-optimal at this stage, as it's a bit too broad and it could be improved in a number of dimensions.)

anyway, hdactl writes the settings on demand by the system.

the "right" solution would be to know what you want to achieve and figure how we can support it through the web interface. in the setup area, under networking, there are ways to assign static IPs, to add aliases, etc., etc.

maybe it is not too hard to support!?!?

alternatively, we were talking on IRC and perhaps we could have a solution (courtesy of relrobber) to have a setting to "freeze" the dhcp (and perhaps other) settings. that may work (at least for you anyway :D )

this is a sensitive area, as it can impact reliability/stability (a big deal on a server that it's working 24x7 or nearly), so we want to tread carefully!
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Re: What is messing with my dhcpd.conf settings?

Postby rgmhtt » Mon Jan 12, 2009 6:29 am

I will try and join the IRC later today, but allow me to introduce myself.

Robert Moskowitz, currently of ICSAlabs. Co-author of RFC 1918. Co-chair of IPsec when the RFCs came out (3rd group of co-chairs for that workgroup, they are on their 6th grouping now :) ). Creator of the HIP protocol. Contributor to IEEE 802.11i and 802.11s. Past contributing editor to Network Computing Magazine. I have been around computers since '66.

I was part of CIDR and am a BIG adherent subnetting. You, as unfortunately so many in this world assume a /24 for any network. The way home networking will evolve over the next year will require multiple /24s or subnetting of a /24 to /26s. Think all the home automation (like 802.15.4 that I have also worked on, but this is more IPv6 than IPv4) and entertainment that is coming on line and the lack of real QOS. Do you know that you can only allow a delay of 10ms from the time you hit your wireless electric drum until you hear it in your wireless headphones? This is a physiological hard limit, and a large file transfer will ruin your timings. This means a separate 802.1Q vlan and at best a separate IP subnet. Similar issues with VoIP.

So a few advanced options now will get you ready for this new evolution. Note I work on standards. Next week is IEEE 802.11 (and .15-.23) in LA.

So I understand your need for simplicity but I also know the need for flexibility.

So let's consider my subnet with a /28 address allocation ( That is 16 addresses (14 usable) or 2^4 so 32-4=28 or 256-16=240. Now since I supplied my server fixed IP address as, that automatically puts the network at an no usable IP address can be higher than For dhcp clients I might might want 183-190. Quite a bit different than your defaults. ;)

It would be nice to get into your database records and dittle the values to get this sort of dhcpd.conf file. But really this is just the start. It is 'good enough' for an advance option button on your config panel. But at this point I really only want to turn off the auto create of dhcpd.conf as I work out a fuller dhpcd.conf that will support multiple subnets. As I indicated above, I already have LOTS of subnets to map over my vlans for traffic isolation.

I will resume this post on the developer's forum where it won't clutter up readings for people that jsut want to get basic functions working....

Thank you for everything you have done todate!

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