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subnetting for local networks

Posted on 2008-10-27
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ok thank you but i have a comment, i feel this is usflul only for internet providers, because why an organisation want to make all its computers IP addresses public ?

and if i got a public ip address and subneted it will all ip addresses that will be generated from that will be public also ?

and about the ip address range i mentioned in the example how come its public i mean it can be local i can assign it in the range for local network when installing the dhcp server right ?

thank you, i will post these questions in a new related qestion do yu can gain more points :)



regards
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Question by:Pure_Heart
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6 Comments
 
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Expert Comment

by:houssam_ballout
ID: 22811076
well, the reason for giving each computer a public IP address for security reasons, bandwidth also.
but it cost  a lot.
if you get a public ip address , you could subnet it to a rang of computers, which every PC would have  a private ip address.

For the private address, it would take the range that you give it.
you must differentiate between public and private ip address, when one of the local computers send packet to the Internet, then the source of that packet will be the public ip address.

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by:from_exp
ID: 22811091
hm...
I would suggest using private addresses where possible, even in DMZ and map appropriate services on the firewall to the real addresses.
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slinkygn earned 500 total points
ID: 22811113
Classless vs. classful subnetting doesn't actually have very much to do with public vs. private networks.  If it were only useful for Internet providers, then we'd all still use it, because the IP system has to work the same everywhere -- you can't have one system for providers and one for everybody else.  But it's still very useful for organizations that have many computers and want to separate them into subnets.

"and if i got a public ip address and subneted it will all ip addresses that will be generated from that will be public also ?"

As I mentioned, how you subnet has little to do with public vs. private.  Yes, if you subnet a public address space, the resulting subnets will also be in public space.

"and about the ip address range i mentioned in the example how come its public i mean it can be local i can assign it in the range for local network when installing the dhcp server right ?"

The range you mentioned was 135.120.x.x.  That range should never be used for a local address space -- simply because some network on the Internet is bound to have that assigned as its public address space, and if your local network uses the same numbers, you'll never be able to get to them.

So for private addresses, you need to use a range that is guaranteed to not be used by any public computer.  The IANA has defined three ranges to be used exclusively for private addresses, in this fashion: the 192.168.0.0/16 subnet, the 172.16.0.0/12 subnet, and the 10.0.0.0/8 subnet.  Any others are invalid private addresses.

Hope that helps!
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Author Comment

by:Pure_Heart
ID: 22811383
thanks slinkygn
ok so what you mean by 192.168.0.0/16  what l16 means ?
also to subnet a network what setting i need to do to dhcp ? just the ip range and the mask ? no additional setting for server or client ?
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by:houssam_ballout
ID: 22811466
CDR
the number of 1 in the subnet
so the subnet is 11111111.11111111.00000000.00000000 which is 255.255.0.0

you must use the public IP from the ISP with its subnet mask and DNS
client is configured  to get DHCP ip
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by:from_exp
ID: 22811468
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