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  1. #1
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    Class A vs Class C Ips and the advantage or disadvantage

    What are the Advantages/Disadavantages of Regular Class A Ips and a Class C Block?

    I see that we can get 5 ips, I assume that they are Class A, I also see that we can get Class C blocks. Is there an advantage to having one over the other if so what is it? Also how many ips are there in a block?

  2. #2
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    Class C block is 256 address, Class A is some huge number of address, like 250,000 if i'm not wrong. Class A is for huge networks, like AOL.
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  3. #3
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  4. #4
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    I understand that part, about hosts and networks. But which is better to have? I'd assume that the Class A is, am I correct, or it really doesn't matter, huh?

    How many ips are there in a block?

  5. #5
    http://www.howstuffworks.com/question549.htm States the following :-

    Class A - This class is for very large networks, such as a major international company might have. IP addresses with a first octet from 1 to 126 are part of this class. The other three octets are used to identify each host. This means that there are 126 Class A networks each with 16,777,214 (224 -2) possible hosts for a total of 2,147,483,648 (231) unique IP addresses. Class A networks account for half of the total available IP addresses. In Class A networks, the high order bit value (the very first binary number) in the first octet is always 0.

    Class C - Class C addresses are commonly used for small to mid-size businesses. IP addresses with a first octet from 192 to 223 are part of this class. Class C addresses also include the second and third octets as part of the Net identifier. The last octet is used to identify each host. This means that there are 2,097,152 (221) Class C networks each with 254 (28 -2) possible hosts for a total of 536,870,912 (229) unique IP addresses. Class C networks make up an eighth of the total available IP addresses. Class C networks have a first bit value of 1, second bit value of 1 and a third bit value of 0 in the first octet.
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  6. #6
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    Cool. Got i t. Basically it doesn't matter.

  7. #7
    True, it is just an allocation issue but if you are looking at a 5 IP address, it is not going to make a difference. It is probably part of a Class C allocation.
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  8. #8
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    Theres a few different definitions of "class a" and "class c" generally speaking.

    Usually when someone says a "class c" they actually mean a /24, or a "subnet" of 255 (256) ip's.

    People have broken down IPv4 kinda like this:

    xxx.xxx.xxx.xxx
    AAA.BBB.CCC.DDD

    a class D (non existing) would be a single ip in theory
    a class C would be like having 123.123.123.0-255
    a class B would be like having 123.123.0-255.0-255
    a class A would be like having 123.0-255.0-255.00-255

    I'm not sure which term is correct, only which is used more often i think thats what he was asking .
    Myles Loosley-Millman - admin@prioritycolo.com
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  9. #9
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    I got it now. thanks to everyone that responded. The links were helpful and interesting. I understand now.

    I thought there may have been some advantage to one Class of ips over the other, but technically there really isn't when you're talking about Classes A B and C.

    Again thanks to everyone.

  10. #10
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    you will not get a class a or b any more. what you do want to get is at least a /20 which is usually globally routable and is not going to get ignored by any networks in advertisments.

    anything smaller and you risk getting clipped on advertisements.

    until then - use your providers and when you get the right size get your own and do a massive readdressing - or buy someone that owns one.
    Dedicated Servers
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  11. #11
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    you will not get a class a or b any more.
    We have space in Class A.
    Mike @ Xiolink.com
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  12. #12
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    Really Class A, B, C etc. is not so relevant any more seen as CIDR is used, which does away with classful addressing as it is wasteful.
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  13. #13
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    5 ip's would just be a portion of a Class A or C upstream provider so the choice here is who you want to be your upstream provider. (And I believe you're actually assigned 8 ip's but only get use of 5. This is how our adsl block was setup.)

  14. #14

    class-A, B, C

    Myles and others who said that the use of class designators is no longer current are correct. In the early days blocks were assigned very poorly. Just about anybody with a webhsoting account who wanted to, for example, use SSL, could get a class-C (a CIDR /24) with just a simple email and no cost!

    This means that many of the available pool of IPV4 addresses are still locked up while being virtually un-used.

    I peronally know of people who have /24's which are not routed at all! So they are 255 addresses that are not available for the rest of the world. But no-one can force them to relinquish them!

    I believe it is now not possible to get /24's assigned by ARIN or APNIC so basically you get a /24 as part of a hosting service, or from a bandwidth provider - you are getting a subnet from a larger pool. Strictly speaking this means a true class-C no longer exists.

    John Day
    Toronto, Canada

  15. #15
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    ARIN is actually putting something to vote soon on giving out /24s to individuals. The problem will be companies like Verio will not accept routes advertised as a /24.
    Mike @ Xiolink.com
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  16. #16
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    Good old IANA, let Arin have as many IPs for Americans as they want and shaft the rest of the world by not giving other registries like RIPE hardly any IPs, tremendous.
    Karl Austin :: KDAWS.com
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  17. #17
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    Why would the average individual need a /24? I have a single IP on my cable modem, and use NAT to get 5+ computers on it. It'd be great to have 5 IPs. But short of assigning one of my boxes about 250 IPs, I can't think of a way I'd use a whole /24. And most of my (normal) friends don't have half as many computers as I have.
    (Edited to replace the nonsense with the correct words.)

    Plus, a /24 would fill up the space real quick. Let's say I owned 50.0.0.0/8. If I gave each customer a /24, I could only fit 65,536 (256 ^ 2 -- the middle two octets) customers on it. It sounds big, but if I have a Class A, I'd like to think I could handle more than 64K customers.

    Are you referring to IPv6? In IPv6, I think a typical customer would get 32 bits of address space. (More than in the entire Internet right now.) Since IPv6 has 128 bits, that leaves 96 bits (or 2^96 = 79228162514264337593543950336) available. So people can afford to be wasteful with IPv6. (32 bits is the same as a MAC address, which makes address assignation (is that a word?) much easier.)

    But if they're talking about giving /24's on IPv4, they're definitely smoking something illegal.

  18. #18
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    ip classless

    There is no "I have from a class a / b /c" anymore.. we live in a classless world now.
    Joseph Marcelletti
    Sprynex

  19. #19
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    we live in a classless world, but ...

    not all addresses are created equal

    in some address ranges routing announcements are likely to be filtered if smaller than /20, in other ranges is it traditional to accept smaller routes

    also, the most newly assigned address blocks are suffering les than 100% usability due to out-of-date filter sets in equipment at various sites.

  20. #20
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    Originally posted by KDAWebServices
    Good old IANA, let Arin have as many IPs for Americans as they want and shaft the rest of the world by not giving other registries like RIPE hardly any IPs, tremendous.
    I must say I've never heard an opinion like this expressed. Do you really believe that IANA more readily allocates new /8 blocks to ARIN than to APNIC or RIPE?

    The converse grumbling I've heard over here is that RIPE makes it too easy to get ISP-sized allocations. In fact, I have some personal experience which seems to bear that out.

    But regardless, I would expect the RIRs to all be handled in more or less the same fashion.

    Kevin

  21. #21
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    If all things were equal then European hosts could get away with giving IPs out like candy, the same as American counterparts that can give out a /24 without any justification (Apart from your money of course). Over here I have to work my ass off providing justification for a /24 or higher.
    Karl Austin :: KDAWS.com
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  22. #22
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    Over here I have to work my ass off providing justification for a /24 or higher.
    We actually have to do the exact same thing here.
    Mike @ Xiolink.com
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    Advanced Managed Microsoft Hosting
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