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Wireless Networks Thread, Change IP Class from C to B? in Technical; We are starting to run out of IP addresses on our present Class C IP address range (192.168.1.x). I am ...
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    Change IP Class from C to B?

    We are starting to run out of IP addresses on our present Class C IP address range (192.168.1.x). I am planning on switching to a Class B IP address range (172.17.x.x).

    Below are the steps I was planning on following. Is there anything I have missed or should any steps be done in a different order?

    1. Change DHCP lease time to 30 minutes so that the new IP addresses will be picked up quickly.
    2. Change router IP and DNS server address on router.
    3. Change DC IP and change the address for the DNS server on DC. (Our DC also runs DNS and DHCP).
    4. Create a new DHCP lease range, delete old range.
    5. Change IPs on printers and access points.

    Do I need to delete the records in the DNS server or will they automatically update?


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    FN-GM's Avatar
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    Change DHCP lease time to 30 minutes so that the new IP addresses will be picked up quickly
    There is no need. once you have your new range on your DHCP when you reboot the client it will pickup the new address instantly.

    I would remove the DNS records, but thats me. You might also need to change the reverse lookup zones. Also you might need to make changes in AD of sites and Services.

    Also change the IP address settings in your printer settings on the clients.

  3. Thanks to FN-GM from:

    netadmin (3rd August 2009)

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    powdarrmonkey's Avatar
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    I wouldn't bother changing class (since CIDR is in common use now, and you have a private IP range anyway, I would just extend your subnet mask).

    Use a CIDR calculator to find a good balance. A mask of (or in CIDR notation, will give you 4,094 usable addresses ( - Just ensure this doesn't overlap with any other addressing scheme you have or are in contact with, like an area network.

    See RFC 1918 (rfc1918) - Address Allocation for Private Internets, RFC 1519 (rfc1519) - Classless Inter-Domain Routing (CIDR): an Address Ass

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    netadmin (3rd August 2009)

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    GrumbleDook's Avatar
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    If you are going beyong 1024 addresses (or in CIDR) or sticky with the move to a class B range is to investigate super-netting and making use of your core switch for routing rather than your normal router. A good layer 3 design will be needed.

  7. Thanks to GrumbleDook from:

    netadmin (3rd August 2009)

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