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Marc-Andre R.
Asked: 2009-11-26 11:41:43 +0800 CST

How to extend IP Range from 192.168.1.1 to 192.168.2.254

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Here's my question. I currently have a network setup to have Static IP manually assigned between 192.168.1.1 and 192.168.1.99 and the rest (192.168.1.100 through 192.168.1.254) assigned automatically by DHCP server hosted on a IPCop server.

Now, I'd like to expand my DHCP range in the 192.168.2.xxx so that I have 254 new slots for DHCP.

First, is this possible to have a DHCP Range splitted between 192.168.1.xxx and 192.168.2.xxx, if so, how to do it (remember i'm using IPCop), if not, what are my others possibilities?

Thank you very much in advance for your help.

networking

5 Answers

  1. Best Answer

    This is going to be slightly tricky if you're intending to treati this as one big subnet, because 192.168.1.0 to 192.168.2.255 isn't correctly aligned on the right boundary for a /23 subnet, so you can't treat it as 192.168.1.0/23.

    If you're completely set on using specifically 192.168.1 and 192.168.2 then you'd need to use a subnet of 192.168.0/22, which is actually the range from 192.168.0.0 to 192.168.3.255. Mostly that just means changing the subnet mask on your whole network to 255.255.252.0

    However once you've done that your DHCP server should be perfectly happy serving IPs from the continuous range 192.168.1.100 to 192.168.2.254.

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  2. Don't know for IPCop, but Microsoft DHCP scopes can be larger as you want; you can't resize them, though, so if you want a bigger scope you need to drop the existing one and re-create it.

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  3. if you do this in windows dhcp you'll actually create a super scope because you'll be creating a scope that spans your current subnet boundary. you'll wind up with two scopes. i'm assuming ipcop will do the same. you'll need to configure routing for clients on each scope to be able to communicate with each other.

    my recommendation would be to create a new scope with a subnet mask that meets your current and future host needs.

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  4. IPCop appears to use dhcpd, which will give you an error when you try a configuration that has multiple dhcp address pools on the same interface. You'll need to use the 'shared-network' declaration like this in the dhcpd config:

    shared-network somename {
    subnet 192.168.1.0 netmask 255.255.255.0 {
        option routers 192.168.1.1;
        range 192.168.1.100 192.168.1.254;
    }
    subnet 192.168.2.0 netmask 255.255.255.0 {
        option routers 192.168.2.1
        range 192.168.2.2 192.168.2.254
}

    Once the pool 192.168.1.100 to 192.168.1.254 is all assigned, dhcpd starts using 192.168.2.2 to 192.168.2.254. Of course, you'll need to add a second router ip address on the same interface (192.168.2.1 in the example above) since the class C netmask (255.255.255.0) prevents 192.168.1.x subnet hosts from seeing the 192.168.2.x subnet hosts and vice-versa - thus there must be a router on the each subnet. If that doesn't suit your requirements, you could consider using a different netmask - i.e. 192.168.0.0 with netmask 255.255.253.0 makes a subnet from 192.168.0.1 to 192.168.3.255.

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  5. Below sample config which is used in CENTOS 6.4 with DHCPD server.

    subnet 192.168.0.0 netmask 255.255.252.0 {
            option routers 192.168.1.1;
            option domain-name-servers      8.8.8.8,208.67.222.222;
            option subnet-mask              255.255.252.0;
            range           192.168.1.2 192.168.2.254;
            filename                "/pxelinux.0";
            default-lease-time      21600;
            max-lease-time          43200;
            next-server             192.168.1.1;
    }
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