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Changing a subnet

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14 replies

by kingofthenerds

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Hi All,

I have a problem, I have an IP range of 192.168.1.* with
a subnet of 255.255.255.0. But i have nearly reached
250 machines.

This means i am out of IP addresses. What can i do to
fix this. What would be the best solution without
breaking the network segment with a router?

Can you give me indepth detailed instructions on how
to achieve this and you will recieve the points.

Thanks

14 replies

by pierrejamme

Not a TCIP expert, but I think if you change your mask to 255.255.0.0 you can have numbers in that range also.
192.168.20.1 etc. You will need to do routing of course.

by jimklallsoo

You can either change the range to

192.168.X.X ---subnet 255.255.0.0

Affording 255*255 nodes

10.x.x.x. ---subnet 255.0.0.0
Affording 255*255*255 nodes

However as Pierre states you would still be better to put a router in place to route the traffic cutting on unnecessary network overhead.

HTH

by cg it

ok, the big question is how many machines are you going to have? and how many machines do you want per subnet. the formula is 2n-2 where n= the # of bits in in the subnet mask field.

A subnet mask 255.255.224.000 Class B [140.x.x.x] yields 6 subnets with 8k+ nodes per subnet.

for a primer on TCP/IP addressing, heres a link:
http://www.hlug.org/presentations/tcpip/tcpip.html

by cg it

remember an address is a combination of both the IP and subnet mask where the subnet mask in a Class C 255.255.255 equates to the network address [24 bits] and the 0 [8 bits] equates to the host address . you can steal some bits from the 8 bit host address to subnet out the Class C. Depending upon how many subnets you want and nodes on the subnet determines the # of bits you'll steal from the host portion of the subnet mask.

Binary 1 1 1 1 1 1 1 1
Decimal 128 64 32 16 8 4 2 1

Maximum Number of Networks and Hosts per Network
Class Default Subnet Mask # Networks hosts
A 255.0.0.0 126 16,777,214
B 255.255.0.0 16,384 65,534
C 255.255.255.0 2,097,152 254

So as you see with Class C your limited to 254 hosts [256-2]

by ctmoore1998

Don't know what your domain type is or if you have any WAN connections and what their IP schemes may be. But if you have a 2000 domain you should be able to modify you subnet starting at the domain controller modify your subnet to 255.255.252.0 will give you a network from 192.168.0.1 to 192.168.3.254 which will give you 4 times as many machines. Just make sure no WAN fall in this network. Every static or manually configured device will need to have it's subnet updated. Don't forget to update DHCP properties on the DHCP server for the DHCP clients. then do a release and renew. Important that you start from the server down as browser elections may be forced by the different subnet sizes until all devices are updated.

by sgt_shultz

yee-ha.
you perfer to change 250 devices subnet mask and ip addresses. rather than install router, eh?
this has to be a textbook question?
you have detailed ip map of network showing every device, it's ip, subnetmask and gateway settings and dhcp client or static.
what about decreasing tcpip lease time from the dhcp server. would that juggle the available addresses some

by kingofthenerds

Not a textbook question and also not that difficult considering most devices are already assigned DHCP. Only about 30 with static IP addresses.

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