Hot!IP Subnetting Issue

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ronzoni01
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2012/09/13 10:06:11 (permalink)
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IP Subnetting Issue

It' s been 5 years since I' ve studied/brushed up on my subnetting skills so i' m a bit rusty. I have run into an issue in one of my offices. The main interface is currenlty running on 192.168.5.1/255.255.255.0 for about the last 4 years. We have since doubled our staff in the office and between the servers, phones and employees, we' ve quickly run out of IPs.

I' m trying to expand the network now so I can at least double the IP Space available.

Using classless ip routing, can I expand the network to allow for 510 maximum addresses by adjusting the interface to 192.168.4.1/255.255.254.0? Would I run into any issues? We' re currently using a FortiGate200A Firewall if that matters.

If this would work, I could simply adjust the default route to 4.1 and update the DHCP server to include the new addresses.

I thank anyone ahead of time for responding.
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    ronzoni01
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    RE: IP Subnetting Issue 2012/09/13 10:08:35 (permalink)
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    not sure how that triple post just happened!
    #2
    rwpatterson
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    RE: IP Subnetting Issue 2012/09/13 11:12:47 (permalink)
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    You really wouldn' t need to change the default gateway. So it' s in the middle...it will still work. What you are proposing looks valid from my end.

    -Bob - self proclaimed posting junkie!
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    #3
    ronzoni01
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    RE: IP Subnetting Issue 2012/09/13 11:26:53 (permalink)
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    Thank you rwpatterson
    #4
    emnoc
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    RE: IP Subnetting Issue 2012/09/13 22:16:14 (permalink)
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    Changing the mask on the FGT is just one step, but all of the existing host would need their masks adjust to /23.


    This is simple to do in a DHCP env, but if you have the 1st 254 adddress hardcoded, you might seen some long hours.

    PCNSE,  NSE , Forcepoint ,  StrongSwan Specialist
    #5
    ronzoni01
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    RE: IP Subnetting Issue 2012/09/14 08:12:46 (permalink)
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    Yes, I need to update the DHCP server settings and then update our site-to-site VPN connections as well as any local servers.
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    ronzoni01
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    RE: IP Subnetting Issue 2012/09/17 11:06:03 (permalink)
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    ORIGINAL: rwpatterson

    You really wouldn' t need to change the default gateway. So it' s in the middle...it will still work. What you are proposing looks valid from my end.


    rwpatterson, a quick question. You state that I could leave the default gateway in the middle. would that means i leave the interface settings the same but just change the Netmask portion of it?

    change it from 192.168.5.1/255.255.255.0 to 192.168.5.1/255.255.254.0 ?
    #7
    abc987
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    RE: IP Subnetting Issue 2012/09/17 11:45:37 (permalink)
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    Your new network is 192.168.4.0/23. It' s not necessary that your gateway is at the first IP (192.168.4.1) or the last (192.168.5.254). So you can left your Interface-IP on 192.168.5.1, only change the subnetmask to /23 (255.255.254.0)
    #8
    rwpatterson
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    RE: IP Subnetting Issue 2012/09/17 15:37:27 (permalink)
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    Both correct.

    -Bob - self proclaimed posting junkie!
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    #9
    byrann21
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    Re: RE: IP Subnetting Issue 2019/02/04 09:57:36 (permalink)
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    I found that discussion useful.
    #10
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