Forum Moderators: phranque
If I understand it correctly an IP address consists of 8 octets. There are class A IP addresses, class B IP addresses and class C IP addresses.
class A: first octet = network, octet 2-4: hosts ...used for very large organizations
class B: first two octets = network, octet 3+4: hosts ...used for colleges, etc. (mid-sized networks)
class C: first three octets = network, octet 1: hosts ...used for small businesses, etc.
Hope I understood this correctly. Obviously it makes sense, because there aren't that many large organizations thus one octet should be enough to identify the network, etc..
But now....why do SEOs talk about links from unique class C IP addresses instead of just talking about unique 'IP addresses' (when trying to assess the quality of a link profile)?
Are they making the assumption that every link they get is from a class C network? Obviously if you get a link from an .edu website it's usually not from a class C network and thus not from a class C IP address, right? wrong?
It seems to me that 'class C IP address' just sounds cooler than 'IP address' thus many SEOs are using it, though the 'class C' part could be left out.
Am I right or am I making a mistake in my reasoning?
thanks!
If you get
For example
host A assigns ips on the cblock - 64.235.234.#*$!
host B assigns ips on the cblock - 234.255.121.#*$!
Your site has the IP of 84.222.121.1
IF all of the inbound links to your site came from IPs within the the two ranges above it would look VERY unnatural. It would be easy to tell that those IPs all reside at just two different hosting providers.
Having IPs pointing to you all from different C blocks shows or at least looks like you are getting links from all over the place which is natural.
There is at least one Google patent I know of that talks about this specifically. I don't have it in front of me, but if my memory hasn't failed me it basically talks about looking at links from the same or similar sites and discounting them. One of the criteria used to determine this was if the IPs were within the same C block.
The reason they're called octets is because each consists of eight binary data bits. For convenience, we express them as four decimal number groups, each ranging from 0 ( (2^0)-1 ) to 255 ( (2^8)-1 )and separated by periods. But in reality, they are sent as binary digits, 0 or 1, "off" or "on." The IP address above actually represents the binary sequence
1100000 10101000 00000000 00000001
Class A, B, and C are fairly straightforward, with class A designating networks which use ranges that vary in their least-significant 3 octets, class B ranging in the last two octets, and class C ranging in the least-significant octet only. However, class D is "special" in that it is broken down into several odd-sized chunks, some of which, such as 192.168.x.y, 10.x.x.x, and 127.x.x.x are reserved as non-routable addresses for use in private networks and subnets. I said "odd-sized" because note that even these three reserved ranges vary in size.
Now to your main question: The reason SEOs talk about class C networks is that they theorize that the search engines use the 'relatedness' of the IP addresses of sites that link to you as a quality factor. So, they posit that having links which all come from the same Class C is not as good as having links that come from different Class B and Class A ranges.
Taking this one step further, almost everyone would agree that if all of your links (or a majority) came from the exact same IP address, then that would look quite 'iffy' to a search engine -- The likelihood that the links all came from a single server hosting sites all under the control of a single organization is high. So, this could be a "link quality" factor, since it is a flag for a potential link network.
Sites with a majority of links all coming from the same class C address would be only slightly less suspect, because that means that all linking sites are within the same range including only 256 hosts -- although of course these could be shared servers, so that could include many more "web sites" than just 256.
Generally, sites which are obviously useful, unique, and of high quality need have no concern about these issues. Only sites which are playing the 'link farm' and 'purchased links' games need worry about it.
Since this is primarily an Apache-server-oriented technical forum, you might want to ask for additional information and opinions in our search engine forums, since it's really an SEO-related question.
Jim
thanks for the replies. I understand the SEO reasons behind that, I was just wondering why they always said 'links from different C class IP addresses' instead of simply saying 'links from different IP addresses'.
I'll read through your replies again..that should be enough for me to understand it! thanks
So, given the huge number of IPs, two links being in the same C class significantly raises the odds that the links are from the same provider with multiple sites. A crude but effective way to discount my dozen sites from all linking to my money-making site.
I was just wondering why they always said 'links from different C class IP addresses' instead of simply saying 'links from different IP addresses'.
It's likey just an easy disticnction between a Class C change and a Class D change(the later, which is much more common).
I would suggest some poking around with ARIN as visitors come through your website doors, as a means to broaden your understanding of IP utilizations.
There are still some major providers that have not broken either their customers or regions down to smaller sub-net assignments. There's simply NO consistencty in the use and/or assignment of IP's.
As to the other generalizations concerning Class C assignmnets?
Most everything stated seems to be general assignment policies in North America, however Europe on the other hand will simply throw your "generalizations" into the nearest trashcan.
I've providers customers in Class C and then returm a few moments later utilizing the same provider from an entirely different Class A.
