August 6th, 2003, 05:35 AM
ip address classes question
I am wondering if it is possible to use a class B or C address ip as a class A. I know about subnet masks and stuff. But im wondering if you could use a network address such as 192.0.0.0 and subnet mask 255.0.0.0, and if there is a way it could work.
If it won't work is it just because the OS will give an error or the router/switch won't exept those configurations. Im thinking if you can subnet, and barrow bits why couldn't you take away bits.
August 6th, 2003, 05:37 AM
No I dont believe it will work each class has their ip range and respective subnet mask.
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August 6th, 2003, 05:46 AM
The IP address 192.0.0.0 must have a subnet mask of 255.255.255.0 then from there you can break it donw futher from that same IP class. So I agree with fl34bit3 on this one, I don't believe you can subnet a class c or b into a class a.
August 6th, 2003, 08:31 AM
*Moved from AntiOnline: How do I?*
August 6th, 2003, 09:17 AM
ah yes IP ranges
Yes you can set any number to your own class C network except for 0, 1, and 255 theses are left open for broadcast. Now dont get me wrong im not saying your isp or your cable provider will provide you with an ip of 10.51.5.13 or let you run a static address, when its running a class B network. But if you are running a router or AP or any other device which allows you to set the subnet mask and the ip range then you can absolutely run your class B or C network with an A address. I would also like to point out that I have seen it with my own eyes and found this very odd myself. also if you think about it, this would make a very good security tactic.
August 6th, 2003, 10:04 PM
sure you can its called CIDR ( Classless inter-Domain Routing) or Supernetting. Its just like Sub Netting But you go the other way for a more detailed explination you can look and any CCNP (Sybex or Cisco) BSCI ( Building Scaleable Cisco Internetworks) book or try this link.
August 6th, 2003, 10:35 PM
Guess I was wrong.
I'm not that advanced yet. I will be in a couple years though.
I'll have to read about that stuff.
August 7th, 2003, 12:41 AM
As stated before by "spetard" this concept is called CIDR (classless interdomain routing)
used by routing protocols only, most commonly the famous BGP4 (Internet standard routing protocol)
I would like to know why you want to do such a thing.
I hope its not because you think you may get more addresses because
that is not the case at all.
Think about it, if you plan on using these addresses on a private network
(not part of the Internet) then you have more than enough RFC1918 addresses
to play with.
If you plan on using the addresses on the public network(Internet), you
will not be able to, because when you apply for an IP address or block
you get only the class A, B or C addresses/blocks ex. (X.0.0.0, X.X.0.0 and X.X.X.0)
Using your example, you would never get just a 192 address from the public domain.
For this reason, as far as I know, unless someone out there can correct me, all
TCP/IP stacks on pc based OS's do not support CIDR and for a very good reason.
Why would you want to. Even if some stack out there did, there would be no usefull
purpose for it.
CIDR again is a concept that is used by routing protocols..
All Internet routers run a standard routing protocol
called BGP4(version 4) that supports CIDR. The reason ISP's use CIDR is to
summarize the routes in the routing table.
Currently there are over 120K routes and growing exponentially
Hope this helps....
Soon to come for anyone new to IP, I am planning on posting a very good tutorial
It Will be a good intro on Ip subnetting and summarization.
August 7th, 2003, 03:53 AM
sodiumwater I i recommned you go to google then there a cisco PDF file that give an information about the whole TCP/IP Protocol thing i dont have the address (exac t) just PM me if you want it OKIE
August 7th, 2003, 06:26 AM
Let's not forget about the fact that B and C class address ranges have significantly less host address available than Class A's do. Class A's have 16 million+, B's have 65,000+, and C's have 255. This to me would be the biggest reason why you wouldn't be able to do it.