Increasing IP Address scope DHCP

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This topic contains 4 replies, has 5 voices, and was last updated by  Anonymous 5 years, 8 months ago.

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  • mrkhbz
    Member
    #161170

    Hi all,

    I have just one DHCP server that is configured with 192.168.x.x ip with subnet of 255.255.255.0, but now I am running out of IP addresses. Will changing my subnet to 255.255.254.0 automatically solve my problem or are there other things that I have to look into?

    Also, someone told me that it is preferred to use the ip class with 172.16.x.x because a lot of hardware vendors use 192.168.x.x by default and this may cause conflicts with as I try to configure new hardware. Any truth to this?

    Thanks! :)


    tehcamel
    Moderator
    #359172

    Re: Increasing IP Address scope DHCP

    definitely truth to it – look at any consumer grade router.
    they usually use 192.168.0.1 or 192.168.1.1 (rarely, I’ve seen 10.0.0.1)

    if you changed your subnet within your DHCP scope, you’d need to make sure to also change it on any hard-configured device, as well as your routers, switches, printers etc to make sure it all routes correctly.


    Anonymous
    #371477

    Re: Increasing IP Address scope DHCP

    Making that one change to the subnet mask will double the address space you’re using, but if you actually have that many devices all on one common subnet, that’s a LOT of broadcast/ARP resolution traffic. And, there’s not a simple method of controlling who has access to what resources, ’cause there’s no boundary control (inter-subnet routing.) With that many devices, you should break it up into VLANs, to cut down on the broadcast domain size, if nothing else.

    Since you didn’t list the 3rd octet of your address range, I’ll point out that if it isn’t already an even number, it will have to be when the mask is changed. The first value of a ‘supernet’ (which is what you’re doing) can’t be an odd number. For example: if your range is currently 192.168.0.0 / 24. your usable addresses are:
    192.168.0.0 – to -192.168.0.254, with .0.255 used for broadcast.

    If you change the mask as planned, your range goes to:
    192.168.0.0 – to – 192.168.1.254, with .1.255 used for broadcast.

    That extra ‘1’ is only added at the end of the new range, so can’t be there at the start. As for whether to use the range of 172.16… vs 192.168…, that’s really up to you. The 172 option gives you a lot more range to play with if you need it, but both ranges are defined as private, so won’t route on the internet. If you’re worried about ‘defaults’, you should always change defaults as a first step in setting things up, including admin names, passwords, remote access settings, etc. If you’re responsible for controlling a network, make certain no one else (outside your admin office team) can.


    biggles77
    Moderator
    #212870

    Re: Increasing IP Address scope DHCP

    Sorry but what is it with you guys and VLANs once you get more than 254 IPs on a subnet? Even with a 1022 VLANs are a WOMBAT. KISS and leave the VLANs out of the equation unless you want to run a specific security subnet.

    Just MO.


    joeqwerty
    Moderator
    #304004

    Re: Increasing IP Address scope DHCP

    mrkhbz;270799 wrote:
    Hi all,

    I have just one DHCP server that is configured with 192.168.x.x ip with subnet of 255.255.255.0, but now I am running out of IP addresses. Will changing my subnet to 255.255.254.0 automatically solve my problem or are there other things that I have to look into?

    Also, someone told me that it is preferred to use the ip class with 172.16.x.x because a lot of hardware vendors use 192.168.x.x by default and this may cause conflicts with as I try to configure new hardware. Any truth to this?

    Thanks! :)

    Yes. Changing to a /24 will double the number of usable ip addresses.

    Using 172.16.x.x because a lot of hardware vendors use 192.168.x.x by default is bunk. If you have a device that uses an ip address in your range then you reconfigure the device for your network. You do not reconfigure your network for the device.

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