IP addresses
 

I usually have an IP address that starts with 90.xxx etc or 94.xxx from the UK, but lately I have noticed that they have begun with 2.xxx or 5.xxx etc which I've never seen before. Is this/they a new prefix for the UK ?



SHJ

The simplest answer is no, there's no such thing as an IP address allocation to a country.

However, 90.0.0.0, 94.0.0.0, 2.0.0.0 and 5.0.0.0 are all part of the IPv4 address space administered by RIPE NCC, the agency responsible for assigning IPv4 addresses throughout Europe, Middle East and (parts of) Central Asia.

Where possible, contiguous blocks of addresses are allocated to the same region to allow for route summarising in the core internet routers, so this can act to some extent as a "country allocation", but it is not intended as such.

SD

That's interesting SD because I assumed that the reason that Spotify sends me ads in Spanish, and that PayPal always defaults to Spanish, is because they are reading my Spanish IP address. So how do they know that I'm in Spain?

You can tell where (almost) any IP address is, and which ISP is behind it.

After that, it gets trickier. There are certain blocks of addresses that are all in China (for example), but in Europe it's not as clear cut.

Relatively new, yes, 2/8 was given to RIPE September 2009, and 5/8 was given to RIPE in November 2010. There will subsequently be a year or two before they actually start giving out those addresses to the ISPs to allocate to customers.

So yes, they do have a bit of new smell to them. But nothing to worry about, they work just the same as any other IP.

Internet routers these days are beefy, not really a current concern. Plus, with the fact that IPv4 is running out, you can't have too many luxuries like that any more.... sure the big blocks will be given to the local registries to allocate to ISPs, but the registries will become more stingy and give out smaller allocations.

Will become more tricky in years to come with the advent of v4/v6 NAT operating at ISP level etc....

Thanks for the explanations chaps! I hadn't read anywhere that the 2.0.xx and 5.0.xx were being released and/or used. On the subject of geographic IP addresses, I was under the impression that they were so configured as to indicate where the user was, rather like telephone numbers, unless the ISP were temporarily routing via another country for some technical reason ? In simple terms what is the difference between IPv4 and 6 ? What would the advantages be of having non-geographical IP addresses for the masses ?



SHJ

No.

Trying to keep things simple :

A global organisation called IANA allocates primary ranges to regional registries. These ranges are typically /8 in size, i.e. ranging from, for example, 2.0.0.0 to 2.255.255.255.255.

The regional registries then allocate sub-ranges to ISPs, the allocations are typically much smaller, for example /21, so you'd get 2.0.0.0 to 2.0.7.255.

ISPs then make much smaller allocations to their customers.

There are two fundamental obligations on the ISP as far as the public databases go :
(1) Keep their own contact information up to date
(2) Record details of sub-allocations they make to customers

As far as the sub-allocations to, there is no requirement to log full details of customer name or address. Just the size of the allocation you've made to them. The argument being that if law enforcement want to know more, they can knock on your door with a warrant.

The primary reason IPv6 is coming is because we're running out of IPv4 addresses. So the main difference is a significantly larger range of numbers.

IPv4 is 32-bit and hence limited to 4294967296 addresses.
IPv6 is 128-bit and so provides 3.4×10^38 addresses.

The visible difference is that IPv4 addresses are easy to read an remember, for example 10.250.240.130

IPv6 addresses are much longer and are expressed in hex form (i.e. can use characters 0-9 and a-f), for example a full IPv6 could look like:

fd01:abcd:ef01:feed:cafe:babe:dead:beef

(Obviously real IPv6 addresses will be a little more "random" and so harder to remember !)

IPv6 does allow for consecutive series of "0000" to be abbreviated as "::", for example :

fd01:abcd:0000:0000:feed:babe:dead:beef could be written as
fd01:abcd::feed:babe:dead:beef


There are a couple of additional features of IPv6 too, such as SLAAC (Stateless Address AutoConfiguration) which enables IPv6 devices to automatically configure themselves when connected to a network. There are also various features of IPv6 that make them able to be more efficiently processed by routers.

The biggest downside of IPv6 is that the geniuses that invented it decided not to make it backwards compatible with IPv4. They are completely incompatible, and as a result you have to implement one of a number of hodge-podge workarounds in order to be able to access IPv6 from IPv4 or vice versa. The easiest, cleanest and best is dual stack IP (i.e. run both IPv4 and IPv6, most PCs are capable of it these days).... but that assumes your ISP gives you both an IPv4 and IPv6 allocations.... sooner or later, they won't have any IPv4 to dish out any more and so you'll have to use less desirable workarounds.