Where is ISP getting its IP from?

Global IP Allocation Flow

All devices which are on the internet have an IP address. Be it your phone, laptop or smart tv.

We all know the ISP(Internet Service Provider) provides public IP to the router, which gives private IP addresses to them(the devices) through DHCP service.

But who is providing the IP to ISP ?

So the short answer to this is IANA (Internet Assigned Numbers Authority).

IANA allocates the unallocated IP addresses. But to whom ?

To answer this we need to understand a Hierarchy.

Here, I’ll talk about the distribution of IPv4 addresses.

RIR(Regional Internet Registry) eg. APNIC- Asia Pacific Network Information Centre

NIR(National Internet Registry)

LIR(Local Internet Registry)

EU(End User)

fig.1
  1. IANA allocates IP address space to RIRs as per their needs described by Global addressing policies.
  2. RIRs allocate IP address space to IRs — NIR and LIR.
  3. National and Local IRs allocate and assign address space to ISPs and, in some cases, directly to the EU under the guidance of RIRs and in accordance with the policies and procedures.
  4. ISP provides to either EU or to a lower ISP which ultimately provides to the EU(End User).

This is how IP is getting to the ISP.

Now let’s dig into some terms that I discussed earlier.

Regional Internet Registries (RIRs) serve and represent large geographical regions. Their primary role is to manage, distribute, and register public Internet address space within their respective regions. Currently, there are five RIRs: APNIC, AfriNIC, RIPE NCC, LACNIC, and ARIN, although a small number of additional RIRs may be established in the future.

A National Internet Registry (NIR) primarily allocates address space to its members, which are generally LIRs organized at a national level. NIRs are expected to apply their policies and procedures fairly and equitably to all members of their constituency.

A Local Internet Registry (LIR) is generally an Internet Service Provider (ISP), and may assign address space to its own network infrastructure and to users of its network services. LIR customers may be other “downstream” ISPs, which further assign address space to their own customers.

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