# Explanation of what identifies a Class C IP block

Discussion in 'Web Hosting' started by GreyWolf, Dec 6, 2010.

1. ### GreyWolfExecutive VIPJr. VIP

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People hear all the time that if you want to create a large network of sites, it's important that they're hosted on separate Class C blocks. After reading some discussion in a service thread I realized that a lot of people have no idea what a Class C IP address actually is. So for those that don't already know, here is a layman's explanation of IP classes.

IP addresses consist of 4 octets of numbers between 0 and 255.
For Classes A, B and C each octet identifies the Network and Host (Node).

Class A addresses have a first octet between 1 to 126
the first octet identifies the Net.
the second, third, and fourth octets identify the Host (Node).
NET.NODE.NODE.NODE
Class A addresses are for large networks used by very large corporations, govt agencies, etc.

Class B addresses have a first octet between 128 to 191
the first and second octets identifies the Net.
the third and fourth octets identify the Host (Node).
NET.NET.NODE.NODE
Class B addresses are for mid-size networks used by large companies, city agencies, college campuses, etc.

Class C addresses have a first octet between 192 to 223
the first, second, and third octets identifies the Net.
the fourth octets identify the Host (Node).
NET.NET.NET.NODE
Class C addresses are for average networks used by small to mid-size companies or agencies.

Class D addresses have a first octet between 224 to 239
Class E addresses have a first octet between 240 to 248
Class D and E addresses use the octets to identify groups rather than nodes and are used for different purposes than Class A through C networks.

(the numbers in each range seem very random, but they're actually chosen because of the binary values of the numbers.)

There are also some reserved addresses that are routed differently than regular addresses.
Reserved addresses within the A, B and C classes:
10.0.0.0 to 10.255.255.255 private network
169.254.0.0 to 169.254.255.255 private network
172.16.0.0 to 172.31.255.255 private network
192.168.0.0 to 192.168.255.255 private network

Reserved addresses outside the classes are:
0.0.0.0 default route
255.255.255.255 host route

So basically if you want to have Class C IP addresses then you need to be in the range between 192.0.0.0 to 223.255.255.255 excluding any reserved addresses.

If only the numbers in the fourth octet change then you do have different Class C IP addresses, but they'll all be within the same Class C block. If you want to be on different Class C blocks then you need to get IP addresses that are different in the first 3 octets between 192.0.0.x and 223.255.255.x

It really depends on what your doing with your sites whether you need to be on separate C blocks or not. If you have a fairly large network of sites and plan to do extensive backlinking between the sites then your probably better off to have the domains hosted on different Class C blocks. If you have a lot of sites but don't have an excessive amount of backlinking between the sites then just being hosted on different IPs within the same Class C block is possibly sufficient. If you just have a lot of sites that are unrelated and don't really do much backlinking then using a shared hosting account with a single IP is probably good enough.

If you do feel you need to host your domains on different Class C blocks then hopefully this thread will help you out.

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2. ### GreyWolfExecutive VIPJr. VIP

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I actually made this thread in response to a few replies by BHWhosting in his service thread
BHW Hosting - Increase Your SEO Abilities Now.
Since it's so long I didn't want to hijack his thread by posting this reply there.

In that thread BHWhosting makes several statements that are wrong about what a Class C IP address is.

For example
In that post the examples for groups of Class C and Class B ranges that are still within the range that he also identifies as Class A. You can't have it both ways, they have to be either Class A, B or C. In this case all of the examples given are Class A IPs and the explanation of what makes it be Class B or C was totally wrong.

In that example he used the addresses
123.123.321.1 and 123.123.321.2 and 123.123.321.3
Specifically they're Nodes 123.321.1 and 123.321.2 and 123.321.3 in the Class A block 123.

Just to keep it simple lets change the examples to
195.123.321.1 and 195.123.321.2 and 195.123.321.3
Now those are Class C addresses.
Specifically they're Nodes 1 and 2 and 3 on the Class C block 195.123.321.

All blocks between 192.0.0 and 223.255.255 are all Class C Nets, so technically all addresses between 192.0.0.0 and 223.255.255.255 are Class C IP addresses. But for someone who's looking to host their sites on different Class C IP addresses, then having sequential Node addresses on the same Class C network isn't what they're looking for. They're actually looking for addresses on separate Class C blocks.

for example if someone wants to be hosted on different Class C blocks:
WRONG
123.123.321.1
123.123.321.2
123.123.321.3
Not what they're looking for because
all are in the same Class A block.

WRONG
195.123.321.1
195.123.321.2
195.123.321.3
Not what they're looking for because
they are all different Class C IPs, but
all are on the same Class C block.

RIGHT
195.123.321.1
195.123.322.1
195.124.322.1
196.124.322.1
This is what they're looking for because
all are on separate Class C blocks.

3. ### savvyproRegular Member

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Don't want to hijack your thread, but I covered the whole "Class" issue pointing out the errors in the statements that were made as well (I do agree it is a somewhat longish thread)..

Another post that I made in a different thread, should also help in why SEO hosting is suspect. The following is a copy of my post in that thread (see here for the full thread):

Basically put, in order for SEO hosting to work they way it's sold, you'd have to host as if you had access to servers in different countries across the world. Once you get to that level of separation then we can really discuss SEO hosting - the way the idea is sold, but not implement.

I've been waiting for someone to bring up a little glaring problem with Class C usage. But as no one has brought it up I might as well put this stupid concept to death. Classful address ranges stopped being used as the means of dividing up the pool of IP address in 1994. Good luck trying to get a real class C address range today let alone 10 years ago.

From 1994 VLSM (Variable Length Subnet Masking) become the standard way of giving out IP address ranges. Now that's not to say that those who were given real class C IP address ranges stopped using them or can still allocate them today it's just very unlikely that any hosting company offering SEO hosting will actual have any real class C address ranges with a real /24 subnet mask (aka: 255.255.255.0) Which is why I wanted access to a test account to run ifconfig as that is the only way to tell.

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Last edited: Dec 6, 2010
4. ### GreyWolfExecutive VIPJr. VIP

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You're not hijacking this thread at all. The replies you made in that thread and the responses you got in return are what prompted me to enter the discussion in that thread and to make this one.

You gave a good explanation of how to identify the classes in that thread. Since it seemed like it wasn't being understood by some people, I decided it was worth discussing further. It didn't seem like you were getting a reasonable response to your questions in the other thread. I was kind of hoping you might find this thread since you can provide a lot more thorough information.

You also gave the binary values for each class range in your post which also shows how the particular ranges were selected. The binary values show the ranges are less arbitrary than they appear to be in decimal values. Here's a portion of your reply from the other thread since it gives additional info to this thread as well.
I agree. Regardless of which class, if you really need to be hosted in different blocks then the best solution is to host your domains across different hosting companies. If your hosting with one company then they would at least need to have several data centers in different geo locations, and allow you to choose which data center each domain is hosted at.

A lot of SEO hosting companies are a little misleading about what they provide. I think for most people just having unique IP addresses for each domain is sufficient and in many cases that's not even necessary. For people that are looking to separate their domains though, I think having a group of sequential addresses in the same net block aren't accomplishing what they want.

I think this is an important part for people to consider if they're looking for SEO Hosting.
The hosting companies need to be more clear about what they're actually providing if they're advertising to that market.

Thanks for the good information.

Last edited: Dec 6, 2010
5. ### bertbabyElite Member

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How are the Class C blocks used in spamming operations? As I recall the adventures of a spamming colleague of mine having blocks of IPs were critically in staying ahead of AOL and Yahoo. I would assume they wouldn't want sequential IPs either because that would be easier to block by an admin looking to shoot down a determined spammer.

6. ### savvyproRegular Member

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I should add that there are only 8 or so unallocated /8 address ranges, at the rate things are going some say that they will be allocated by early next year.

When that happens, bad use of IP v4 addresses may start to be reined in. IP v6 uptake is not moving fast enough.

When it does take off, I wouldn't be surprised if the SEOhosting pushers start insisting that everything on the site has it's own unique IP address. Today you can get accounts with hundreds of addresses, when IP v6 comes round it could be into the millions.

7. ### HostwindsPower MemberUnGagged AttendeeEnterprise Member

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Because its easier to identify spamming attacks if they all come from the same block....just block the block lol

8. ### paincakePower Member

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By the way, the world is running out of ipv4 addresses:
Code:
`http://twitter.com/#!/ipv4countdown`
There are 109 million ips available right now and this number seems to drop by 3 million every day, so it seems its gonna be about a year before we run out of them. Well, perhaps longer, because a lot of ips are reserved by governments.

9. ### bbob1970Junior Member

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For seo hgosting you might also want to add that besides different c class ip's you need:

different nameservers for the different ip classes
Depending on your domain extensions you might need anonymous registration or different details for google not to see thru this.

Also I have used some of these so called seo hosting offers but 1 advice stay away from them. some of them are cheap but many hosting companies go out of business the first 2 years. So when you finally setup your say 10 or 20 different ip's and the hoster goes out off business you have lots of work to do again.

I am now just buying shared hosting packages from different providers. You can check webhostingtalk.com but be carefull choose ones that have been in business for more thatn 2 years.
A normal shared hosting package should cost between \$12 and \$30 per year. It might a a bit more work getting the from different companies but if one goes out of business you are loosing 1 package instead of all.
When possible try to get a big vps say 20-30 gb that you can use to backup all yourt sites. In the end this will cost a bit more but it works better and reliable.

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