Hardware & IP Question - Non SEO

[T0PS3O]

Question for the Hardware Tech guys and girls:

What is the technical implication of having multiple sites hosted on one IP address and also the same block.

The host we are with has (at least)

98 websites on the exact same IP address like abc.def.ghi.12
10 websites on the exact same IP address like abc.def.ghi.13
and in total 120+ on the same IP block abc.def.ghi.xx(x) (around 10 have their 'private' IP address... Why?)

Regardless of SEO implications... What does this mean technically?
Are they all on the same server?
All on the same physical hard disk?
Do they all share the same internet connection? Or can you not tell?
If the server goes down, do all go down or just those in that block?

What would be the technical advantage of one site being on abc.def.ghi.987 for example (private IP) when all the others are as mentioned above?

Can a subfolder like domain/folder be hosted on a different IP?
Can a subdomain like sub.domain be hosted on a different IP address?

I know it's a lot of questions in one go but I want to gain more insight into hosting and the technical side of it. Can anyone recommend a book by the way or other resources to study about ISP's and hosting providers?

Thanks! Vielen Dank! Dankjewel! Dankewol! Gracias! Cheers!

[digitalpoint]

They would all be on the same server, not necessarily on the same physical hard disk (although it's probable), and they would be sharing the same Internet connection (since you can only throttle/limit bandwidth at the router level based on IP address).

A subdomain can be on a different server, since it can use a different IP address. forums.digitalpoint.com and www.digitalpoint.com are different IP addresses for example.

[T0PS3O]

Thanks for the swift response!

Is it possible to forward a particular IP address to a specific hard disk on a server just like I do port forwarding on my network router at home?

So if the technical environment for all those IP's are the same (apart from the hard disk perhaps), the only reason for allocating a unique/private IP to a particular site would then be for possible SEO reasons as theorized in the other threads wouldn't it? Or could it be something else?

Can one domain name be 'attached' to several IP addresses to 'spread' the load or to geo target or can this only be done after a http request has reached that IP address where it then can be processed and forwarded to the appropriate IP?

[digitalpoint]

Yes, you can setup a server to serve requests for certain sites (not really specific to IP address though) from a certain volume on the server.

There are other reasons for assigning unique IP addresses. For example secure (HTTPS) sites can only have one site per IP.

You can spread a single site across multiple IP addresses for fail over and/or load balancing (every large site does that).

[dsr771]

The IP address just gets you connected to a server. Then the webserver configuration tells which hard drive to find the site on based on IP or domain name. If each website gets its own ip, then that can be used. If multiple sites on a single IP, then the domain name is used.