Results 1 to 20 of 20
  1. #1
    Join Date
    Apr 2003
    Posts
    91

    What is an IP C-class?

    If I had an IP: 66.15.623.110

    Would this IP: 66.15.623.111 be in a different C-class?

    Or, could someone give an example of an IP with a different IP C-class?

    Thanks.

  2. #2
    I remembered that C-class IP's were 192.168.x.x subnets.

  3. #3
    Join Date
    Apr 2003
    Posts
    91
    Originally posted by clanscc
    I remembered that C-class IP's were 192.168.x.x subnets.
    In English please.

  4. #4
    Join Date
    Nov 2003
    Location
    San Francisco, CA
    Posts
    921
    A.B.C.x

    If they say you have a class C, then it would be A.B.C.x

    If they say you have a class B, it owuld be A.B.x.x

    And of course a class A is A.x.x.x

    (the A, B and C octets are fixed/provided to you by your ISP or hosting provider)

    As further clarification, a half-class C would be A.B.C.x with a subnet of 255.255.255.128

    Just an FYI on how that works.
    Adam - AQORN
    Official OpenStack Foundation Member, Corporate Sponsor and AI Research Team
    Our Clients: Facebook | Red Hat | Starbucks | AT&T | HPE | NVIDIA | CrowdStrike | Cisco | Juniper | SAP | Autodesk | SUSE | Ubuntu

  5. #5
    Join Date
    Jan 2003
    Location
    Lake Arrowhead, CA
    Posts
    789
    To (hopefully) simplify a bit more, the x's used above by MrManager represent all numbers from 0 to 255 in that "position". A.B.C.x (where A, B and C are fixed) gives you 255 IP addresses. A.B.x.x gives you 255*255 (sort of).

    Enough with simplicity . . . the first "octet" tells you the class of the network.

    1 and 126 is a Class A address.
    128 and 191 is a Class B address
    192 and 223 is a Class C address
    224 and 239 is a Class D address
    240 and 255 is a Class E address.

    To back up a bit... why are all the numbers from 1 to 255 and what the heck is an octet?

    To understand, you need to know how to count in binary. You probably already know that binary is like switches: 1=on, 0= off. Now put eight switches back to back and start thinking about how high you can count.

    One switch = 2
    Two switches = 2*2
    Three switches = 2*2*2

    Keep doing this until the result is 256 and you'll have 8 switches (okt/oct are greek and Latin for eight). IP addresses are simply four 8-bit "words" (eight switches), joined by dots. Hope that's not too nerdish to be helpful.
    http://www.srohosting.com
    Stability, redundancy and peace of mind

  6. #6
    Join Date
    Oct 2003
    Location
    Georgetown, Ontario
    Posts
    1,771
    omg... this reminds me of my comp engineering class i had a while back when in highschool. lol

    I hated learning about subnets and ip classes and binary crap.
    ·· Repeat after me... ProSupport is the best... Prosupport is... ··
    ProSupport Host Support System - OUT NOW! Grab a copy yourself and see what the hype is about!
    VertiHost Inc. - We run a quality business. Do you?

  7. #7
    Join Date
    Feb 2003
    Location
    Kuala Lumpur, Malaysia
    Posts
    4,980

  8. #8
    Join Date
    Apr 2003
    Posts
    91
    Wow, thanks.

  9. #9
    Join Date
    Jun 2000
    Location
    Washington, USA
    Posts
    5,990
    Good explanation.

  10. #10
    Join Date
    Nov 2002
    Location
    ON, Canada
    Posts
    290
    Which one is right? MrManager or SROHost? I dont know why but I under MrManager's better because when I was doing my DNS first time, it said my DNS are in the same Class C zone and its not right for some reason.

  11. #11
    Join Date
    Apr 2001
    Location
    Pittsburgh, PA
    Posts
    1,306
    Originally posted by ******
    Which one is right? MrManager or SROHost? I dont know why but I under MrManager's better because when I was doing my DNS first time, it said my DNS are in the same Class C zone and its not right for some reason.
    They're both right, sort of. Originally, each of the A, B, and C classes had specific first octets. But people think of A, B, and C classes primarily in terms of the size of the allocation - in CIDR notation, A is /8, B is /16, and C is /24. So the legacy meanings have faded since CIDR is fully adopted, and now when someone says they "have a Class C" they really mean they have a /24 which is probably allocated from old Class A space, technically.

    Kevin

  12. #12
    Join Date
    May 2003
    Location
    Tampa, FL
    Posts
    49
    I think what he means is the scenario required by a few registries like .co.za
    They require nameservers with IP numbers on 2 class C's from what I remember.

    So using his example in the original question:

    If I had an IP: 66.15.623.110

    another class C would (at least) have to be: 66.15.624.110

  13. #13
    Join Date
    Nov 2003
    Location
    San Francisco, CA
    Posts
    921
    Originally posted by fastdatasvr
    I think what he means is the scenario required by a few registries like .co.za
    They require nameservers with IP numbers on 2 class C's from what I remember.

    So using his example in the original question:

    If I had an IP: 66.15.623.110

    another class C would (at least) have to be: 66.15.624.110
    66.15.624.110 ?

    ATTN NexD:
    Try to see why this IP is totally invalid. Look at it closely and see if you can find the problem. You may want to check a previous post for a clue as to why this would be completely bogus in ANY scenario.
    * If you get it wrong, we'll give you a hint as part of your IP training, young grasshoppa.

    Everyone else:
    Let's not give it away folks- let the original poster try and take a stab.
    Last edited by thecloudguy; 01-18-2004 at 08:59 PM.
    Adam - AQORN
    Official OpenStack Foundation Member, Corporate Sponsor and AI Research Team
    Our Clients: Facebook | Red Hat | Starbucks | AT&T | HPE | NVIDIA | CrowdStrike | Cisco | Juniper | SAP | Autodesk | SUSE | Ubuntu

  14. #14
    Join Date
    Jan 2001
    Location
    Illinois, USA
    Posts
    7,175
    I think this would be a more appropriate forum; and this topic might make a great tutorial/how-to: "How-To tell what class an IP is in"

  15. #15
    Join Date
    Apr 2003
    Posts
    91
    Originally posted by MrManager
    66.15.624.110 ?

    ATTN NexD:
    Try to see why this IP is totally invalid. Look at it closely and see if you can find the problem. You may want to check a previous post for a clue as to why this would be completely bogus in ANY scenario.
    * If you get it wrong, we'll give you a hint as part of your IP training, young grasshoppa.

    Everyone else:
    Let's not give it away folks- let the original poster try and take a stab.
    Sorry, been away and didn't see this thread pop up.

    I'm totally clueless, I thought that the first number in the 3rd column just had to be different-- In order to be in a different C-class.

  16. #16
    Join Date
    Apr 2003
    Location
    Ottawa
    Posts
    959
    I dont want to ruin the fun , but...
    ANways its invalid because the third number is 624 and the maximum it can be is 255 (2^8-1 since 0 is counted) .

  17. #17
    Join Date
    Jul 2002
    Posts
    1,443
    66.15.624.110 ?

    Hint take a look at bold =P

    and the following combinations dont exist:

    256
    265
    426

    so the IP should be 246 ?
    Synergy Blue LLC
    SonataWeb.net | SynergyBlue.com
    USA should so something about: http://www.brillig.com/debt_clock/

  18. #18
    Join Date
    Apr 2003
    Posts
    91
    Originally posted by demonmoo
    I dont want to ruin the fun , but...
    ANways its invalid because the third number is 624 and the maximum it can be is 255 (2^8-1 since 0 is counted) .
    Ah, of course.

    255.255.255.0

  19. #19
    '255.255.255.0' is not actually why that doesn't work but you're definately on the right track. The highest possible number in any IP address (IPV4 for the purists) is 255

    One day I'll finish my "IP Address Primer"...

  20. #20
    Join Date
    Aug 2002
    Location
    UK
    Posts
    852
    ^^ I did one already, but it's pretty old:

    Part 3 - IP addressing
    Ugh, the section I hate most, and my hands are getting tired, *******it you all f**king suck.
    IP addresses are 4 8 bit (octet) numbers which represent a unique device on a network.
    You'll find a normal IP address looks like this: 192.168.0.1 .. That's internal, and 216.239.51.99, that's external. now, you have to break this down according to the subnet mask, i'm sure you've seen your default subnet mask of 255.255.255.0 and you haven't got a f**king clue what this means. Ok, first of all, lets see that in binary:
    11111111.11111111.11111111.00000000

    Excellent, now, you'll see IP addresses being represented like this: 192.168.0.1/24.. DONT PANIC (lol hitchikers guide lol), the /24 simply means the number of consecutive bits in the subnet mask, IE 255.255.255.0, /27 would be:
    11111111.11111111.11111111.11100000
    If my binary doesn't fail me, that's 255.255.255.224 .. WHAT DOES THIS MEAN I hear you cry! Well it's simple, the first 27 bits of the IP address determine the network instead of the client, which in turn, means we have less clients per network, infact there is a very simple way to work this out. First we need to know how many hosts we can have with this, well lets see. We are subnetting the fourth octet, and there are 5 host bits (binary 0s), so we do this equation:
    2^5-2
    Which gives us 30, so each network will have 30 hosts in it. (if we decided on a subnet of /28, we'd have 2^4-2 or 14 computers)
    We can also do the same equation with the network bits, 2^3-2, which gives us 6 networks. If you haven't understood any of this, don't worry, you don't have to, but basically, the subnet mask defines how many bits of the IP address are network bits, and how many are host bits, with a subnet mask of 225.225.225.224, we have 6 different networks (give me a minute) and 30 hosts per network.

    We have 6 different networks for the following reason, here is a standard class C address in binary, overlayed onto the mask.


    IP (number): 192 .168 .0 .1
    IP (binary): 11000000.10101000.00000000.00000001
    Subnet Mask: 11111111.11111111.11111111.11100000


    Ok, we have 3 solid blocks of 1s in the subnet mask, so those represent a network address, the last octet represents a subnetted address as it is not solid 0s and not solid 1s. For now we ignore the first 3 octects and concentrate only on the last. There are 3 network bits, and they can be arranged like so:
    000
    001
    010
    011
    101
    110
    100
    111
    Hold on, that's 8 permutations, I thought you said there are 6 networks Mr Winkie! Well yes I did, and this is another minor difference. Under classic rules, we had Class A addresses, Class B, and Class C. You don't have to know about these, but basically, we work on a system called CIDR, Classless InterDomain Routing now, which DOES allow the network address in the last octet to be all 0s or all 1s, so for safety, you have 6 networks, in all reality you can use 8 most of the time, legacy equipment will **** itself but there you go.
    Now you know the basics of subnetting equpment so that you have a reasonable address range for your gear and you can set up multiple networks of a reasonable size, you need to know what IP addresses you can use!
    For this example we'll be using a subnet mask of 255.255.255.224 and the first 3 octets will be 192.168.0
    To find the stepsize, it's very simple, 256-224, or 256-final subnet octet, which gives us 32. If we're following CIDR we can start at 0, so in binary, the IP address could be:
    11000000.10101000.00000000.000xxxxx
    Next we would have to add 32, so it would be
    11000000.10101000.00000000.001xxxxx
    Then
    11000000.10101000.00000000.010xxxxx
    You can see how the different networks are arranged, so what do we do for IP addresses? Well obviously as we're subnetting the final octet, the client address is integrated into the network address. We already worked out we had 30 addresses for each (we removed 2 for a reason I will explain breifly)
    I chose subnetting the final octet as it's slightly tricker, but lets review where we are so far. We know that the network address without the client address is 192.168.0.0,32,64,96 etc, so we must add a client address onto this. This is very easy, there are 2 simple rules you must follow however.
    1. You may not use the lowest IP address in the range (in this case, 192.168.0.0)
    2. You may not use the highest IP address in the range (in this case, 192.168.0.31)
    These two addresses are reserved for broadcast addressing, IE if you send a packet to 192.168.0.31, every computer on the 192.168.0.0 subnet will recieve said packet. This leaves us with, for the first network, the address ranges 192.168.0.1-30
    That's it, you've successfully subnetted a class C network down to 8 (we're using CIDR rules) networks of 30 hosts each. There's only one small section left before I mention how much I hate firestorm!

    Part 3b - MAC addresses
    A MAC (Media Access Control) address, is the physical address of your computer, it's actually coded by network card manufacturer and various other things but that's not important, If you're running windows you can find your mac address by typing 'ipconfig /all' at a command prompt, it should look like this: 00-02-B3-2F-CC-9A.
    IP to MAC resolution (needed for almost all forms of network communication) is done by the Address Resolution Protocol or 'ARP'. You don't need to know much about this, just that your MAC address is unique if it's factory issued, although you can change MAC addresses on a lot of cards, it's a far better identifier than your IP address, several universities will require you connect a card with a specific MAC address to their network and nothing else.
    If you want to see which IP address to MAC addresses your PC knows about, assuming you're on windows, get a command prompt and type 'arp -a'.
    I can't think of anything more you need to know about IP addresses or MAC addresses, other than to say, unless you are setting up a couple of networks or being 'proper' about things, a subnet mask of 255.255.255.0 is fine, and use the network address 192.168.0, this means you have a range of 192.168.0.1-254

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •