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  1. #1
    Master Untangler
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    Default DHCP Lease Range Issues?

    I am running Untangle 10.2.1 in Router mode with a single WAN and Internal interface. Internally we were using 192.168.100.1 with a subnet of 255.255.255.0 (aka /24) using a DHCP Range Start of 192.168.100.81 and DHCP Range End of 192.168.100.254.

    As we are adding more access points, we needed to expand the network so I had switched the subnet to 255.255.254.0 (aka /23) using a DHCP Range Start of 192.168.100.81 and DHCP Range End of 192.168.101.254 (since the the CDIR calculator shows address range being 192.168.100.0 - 192.168.101.255).

    I have placed a support request but not had any resolution, so wondered if you guys had any other ideas as to why only 192.168.100.x addresses are being issued and no 192.168.101.x addresses???

  2. #2
    Untangler jcoffin's Avatar
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    What is the netmask is showing on the DHCP clients? If it is /23, it is working correctly.
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  3. #3
    Untangle Ninja Jim.Alles's Avatar
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    Untangle 9.4.2 has 2.45-1 dnsmasq
    Debian squeeze (Untangle 10) has 2.55-2 dnsmasq
    2.71 dnsmasq has been released - be careful in that the current MAN page does not apply to us - dig the proper one out of an archive.

    reference:
    http://www.thekelleys.org.uk/dnsmasq/CHANGELOG

    Although dnsmasq can handle CIDR, it also makes some assumptions based on the class of a network number (if not given explicit info). What you have done is supernetted two class C networks.

    Untangle does not supply a netmask to dnsmasq. Dnsmasq should figure it out from the interface, however (which might cause a problem for DHCP relay).

    Something that might be cleaner is to subnet a class B network such as 172.22.0.1/16

    Contrary to a common misconception, a /16 subnet of a class A network is not referred to as a class B network. Likewise, a /24 subnet of a class A or B network is not referred to as a class C network. The class is determined by the first three bits of the prefix.
    You can still assign subnets like 172.22.100.1/24, and 172.22.100.1/23 might work better with dnsmasq's default approach.

    I have not tested any of this, just trying to point you in the right direction.

    Jim A.
    Last edited by Jim.Alles; 07-03-2014 at 07:02 AM.
    If you think I got Grumpy

  4. #4
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    Quote Originally Posted by jcoffin View Post
    What is the netmask is showing on the DHCP clients? If it is /23, it is working correctly.
    I get Subnet Mask: 255.255.254.0 showing up on client's, only IP Addresses in 192.168.100.x are showing up, nothing shows up under 192.168.101.x (and yes, we do have more client's than IP Addresses available in the DHCP Lease Range).

  5. #5
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    I think I understand what you are talking about and I have expanded a Class C network from /24 to /23 with Windows DHCP's servers without any issues, just not Linux DHCP's servers. In looking into this, under Untangle 9.4.2 (or earlier), there were options to add multiple ranges using dnsmasq which would do what we were looking for without having to change all the Static IP addresses again but not sure how this maps to Untangle 10.2.1. Anyone know what options are needed or how to add another range?

  6. #6
    Untangle Ninja Jim.Alles's Avatar
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    That's Ok - I am not entirely sure that I know what am talking about - still editing ;)

    I did see that re-numbering as a lot of work on your part.

    Dnsmasq will still accept multiple ranges.

    Under Configuration / network / advanced / DNS & DHCP try

    Code:
    dhcp-range=interface:ethX,192.168.101.1,192.168.101.254,86400
    or maybe better:
    Code:
    dhcp-range=192.168.101.1,192.168.101.254,86400
    Replace ethX with the interface you are using. Remember, bad syntax here can bring dnsmasq to a halt. Again, I have never done this myself.

    If you get into the terminal, it would be interesting to see what /etc/dnsmasq.conf contains.

  7. #7
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    The only option that I can see is the --dhcp-lease-max, wondering if that is set correctly, could not find anything with respect to any defaults, etc. Also, don't see any way of setting it within the UI, seems like it would have to be in /etc/dnsmasq.conf which is probably updated with changes, etc.

  8. #8
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    I will keep an eye on this tomorrow, switched the Range Start to 192.168.100.81 and Range End to 192.168.100.254 and added dhcp-range=192.168.101.1,192.168.101.254,3600 to the Advanced DNS & DHCP Custom dnsmasq Options.

  9. #9
    Untangle Ninja Jim.Alles's Avatar
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    Quote Originally Posted by chmcwill View Post
    The only option that I can see is the --dhcp-lease-max, wondering if that is set correctly, could not find anything with respect to any defaults, etc. Also, don't see any way of setting it within the UI, seems like it would have to be in /etc/dnsmasq.conf which is probably updated with changes, etc.
    dnsmasq v2.52 changelog:
    Code:
    Increased the default limit on number of leases to 1000
                (from 150). This is mainly a defence against DoS attacks,
                and for the average "one or two class C networks"
                installation, IP address exhaustion does that just as
                well. Making the limit greater than the number of IP
                addresses available in such an installation removes a
                surprise which otherwise can catch people out.
    I believe UT 10.0 hardcodes that conf entry of dhcp-lease-max=5000. should be ample.
    Last edited by Jim.Alles; 07-03-2014 at 01:15 PM.

  10. #10
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    Yes, this appears to be working as I am now seeing IP Addresses being assigned on both 192.168.100.x and 192.168.101.x when looking at the DHCP Clients in Untangle and those connected to the Access Points.

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