How ISPs Provide Static IPs

ISPs (Internet Service Providers) provide static IP addresses by reserving a specific IP address for a customer and configuring their network to always assign that same IP. Here's how it works technically and logistically:

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🔧 1. IP Address Allocation

ISPs are assigned blocks of IP addresses (IPv4 or IPv6) by regional internet registries (like ARIN, RIPE, APNIC, etc.). They manage these blocks and can subdivide them for use by individual customers.

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📡 2. Static IP Assignment Process

When you request a static IP:

• The ISP selects an available IP from its pool and reserves it just for you.

• They then configure their DHCP server (Dynamic Host Configuration Protocol) to always assign that IP to your connection (usually identified by your router's MAC address or customer account).

• Alternatively, they may configure the static IP manually on their end and require you to configure it on your device/router.

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🧰 3. How It’s Delivered

• Home users typically get dynamic IPs unless they pay extra.

• Static IPs are common in business plans or hosting environments.

• The static IP can be assigned:

  • Directly to a router/modem

  • Or to a specific server/device behind a NAT using port forwarding or DMZ

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🧪 4. Routing and Configuration

• The ISP sets up routing rules in their network so that traffic destined for your static IP is directed properly.

• This might involve:

  • Configuring ARP tables

  • Updating routing protocols

  • Adjusting firewall rules or reverse DNS settings

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🧍 Example:

You pay your ISP for a static IP, and they assign 203.0.113.42 to your connection. Every time your router connects:

• The ISP's DHCP server recognizes your account or MAC.

• It assigns 203.0.113.42 instead of a random dynamic IP.

• The router (or device) is configured to expect that static IP.

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💡 Why Use Static IPs?

• Hosting websites or email servers

• Remote access (VPNs, RDP)

• Reliable DNS mapping

• Security & firewall configurations

Would you like to see how to configure one on a router or operating system?

Great question! The IP addresses that ISPs use are allocated by regional internet registries (RIRs), which operate under the oversight of a global authority. Here's the breakdown:

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🌍 1. IANA (Internet Assigned Numbers Authority)

• Top-level authority responsible for managing the global IP address space.

• Operated by ICANN (Internet Corporation for Assigned Names and Numbers).

• IANA allocates large blocks of IP addresses to Regional Internet Registries (RIRs).

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🌐 2. RIRs (Regional Internet Registries)

There are five RIRs, each responsible for a specific region of the world:

• RIRs receive large IP blocks from IANA and distribute them to ISPs, governments, corporations, and educational institutions.

• They also manage ASN (Autonomous System Numbers) and support routing policy.

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🏢 3. LIRs (Local Internet Registries) – Typically ISPs

• ISPs apply to their respective RIR to become a Local Internet Registry.

• As LIRs, ISPs receive IP address blocks to assign to their customers.

• They must justify their need for more IPs (usage, network growth, etc.).

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🛠️ 4. IP Address Types ISPs Receive

• IPv4 addresses: Still widely used, but very limited (most RIRs have run out of large pools).

• IPv6 addresses: Much more abundant, being increasingly deployed.

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🔁 Summary Flow:

IANA → RIR (e.g., ARIN) → ISP (e.g., Comcast) → Customer (static/dynamic IP)

Let me know if you'd like to see how IPv6 allocation differs or what ISPs do when IPv4 is scarce.

Yes — globally routable IPv4 addresses are assigned to LIRs (usually ISPs, data centers, etc.) by RIRs, and these assignments are coordinated to ensure that each address is unique on the global internet.

Here’s how it works in more detail:

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✅ Globally Unique IPv4 Addresses

• Every public IPv4 address must be globally unique so that data sent over the internet reaches the correct destination.

• To ensure this, IANA → RIR → LIR → End User follows a structured and hierarchical distribution model.

• Once an IP block is assigned to a LIR (ISP), that LIR owns the right to use it and advertise it via BGP (Border Gateway Protocol) on the global internet.

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🌍 What "Globally Assigned" Means

• The IPs are registered in public WHOIS databases managed by the RIRs (e.g., RIPE WHOIS, ARIN WHOIS).

• Anyone can look up an IP and see which organization it was allocated to, ensuring transparency and coordination.

• This global registry system prevents IP address conflicts, which would break routing on the internet.

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🚫 Private (Non-Global) IPv4 Addresses

Not all IPv4 addresses are globally routable. Some are reserved for private/internal use:

These addresses are not assigned by RIRs for public routing — they’re used within local networks behind NAT (Network Address Translation).

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📉 IPv4 Scarcity

• IPv4 addresses are nearly exhausted globally.

• RIRs now issue only small allocations or reclaimed IPs.

• Organizations buy/sell IPv4 blocks on secondary markets (e.g., IPv4 brokers), with approval from the relevant RIR.

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🧭 Summary:

Yes, globally routable IPv4 addresses are assigned to LIRs (like ISPs) by RIRs, and this allocation is managed at a global level to ensure uniqueness and proper routing across the entire internet.

Would you like to see an example of how to trace an IP to its LIR or check its global routing status?

Exactly — when your ISP assigns you a static IP address, no other ISP anywhere in the world should be using that same IP address (assuming it's a public IP, not a private or CGNAT one). Here's why:

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✅ Public Static IPs Are Globally Unique

• Your static IP comes from a globally assigned, routable IP block owned by your ISP.

• That IP is registered in global routing databases and announced via BGP (Border Gateway Protocol).

• Other ISPs and networks use this routing data to ensure traffic to that IP goes only to your ISP — and ultimately, to your device.

So yes:

If it’s a public static IP, it is guaranteed to be unique globally.

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🚨 What About Duplicate IPs?

There are only a few scenarios where IP address duplication might occur:

1. Private IP addresses (e.g., 192.168.x.x, 10.x.x.x)

   • These are reused everywhere, behind NAT.

   • Your home and a corporate office in another country could both use 192.168.1.100 — but they aren’t visible to the public internet.

2. Carrier-Grade NAT (CGNAT) IPs (100.64.0.0/10)

   • Used by ISPs to share one public IP across multiple customers.

   • These are also reused internally and not globally routable.

3. IP Misconfiguration or Hijacking (Rare)

   • Misconfigured networks or malicious actors could advertise an IP they don’t own.

   • BGP filtering and RPKI help prevent this, but it’s still a potential issue.

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🧪 How to Check Your Static IP’s Ownership

You can look up any public IP address using a WHOIS or IP lookup tool:

• RIPEstat

• ARIN WHOIS

• ipinfo.io

These will tell you:

• Which ISP owns the IP block

• The country/region

• Whether it's being advertised on the internet

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🧭 Final Thought

So yes — when your ISP assigns you a static public IP, it is guaranteed to be globally unique, and no other customer (of any ISP) should have that same IP at the same time.

Want me to walk you through verifying your current IP's owner and routing status?

That's an excellent question — and actually, we have effectively run out of new IPv4 addresses, including static ones. But the reason you can still get a static IPv4 address from your ISP comes down to reuse, conservation, and a few workarounds. Let’s break it down:

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🛑 1. IPv4 Exhaustion Happened Already

• IPv4 has about 4.3 billion total addresses (2³²).

• Subtract unusable/reserved blocks (e.g., multicast, private ranges), and fewer are actually available.

• The last big free pools of IPv4 addresses were allocated by IANA to the RIRs in 2011.

• Since then, all five RIRs have exhausted their pools (some still give out tiny fragments).

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🧩 2. Why You Can Still Get a Static IPv4 Address

✅ ISPs Already Own IPv4 Blocks

• ISPs received large blocks of IPv4 addresses years ago.

• They recycle and reallocate those IPs as customers come and go.

• When you get a static IP, it’s likely one they’ve used for someone else before.

🔄 IP Address Reuse

• Static IPs are only assigned when requested.

• Many customers are fine with dynamic IPs or use CGNAT — freeing up static IPs for others.

🛒 IPv4 Market Exists

• Organizations buy and sell IPv4 blocks now.

• ISPs can purchase IPs from others on secondary markets.

• Example: Microsoft once bought millions of IPs from bankrupt Nortel.

📦 Subnetting and Efficient Allocation

• ISPs use subnetting (splitting large blocks into smaller chunks) to use IPs efficiently.

• Small businesses may get just a /30 (4 IPs), not a whole /24 (256 IPs).

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💡 3. Other Tricks to Stretch IPv4

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📉 4. Why Static IPv4 Is Getting Rarer & More Expensive

• Because they’re finite, static IPv4 addresses are a limited resource.

• ISPs often charge extra for static IPs or limit how many you can get.

• Some smaller ISPs or cloud providers might not offer them at all unless you justify the need.

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🧭 Final Thought

So while we have technically run out of new IPv4 addresses, recycling, NAT, secondary markets, and careful allocation allow ISPs to continue offering static IPv4 — for now. Long-term, the solution is IPv6 adoption, which has 340 undecillion (3.4 × 10³⁸) addresses.

Would you like to see how IPv6 solves this problem differently?

Yes, ISPs do implement NAT (Network Address Translation) — especially Carrier-Grade NAT (CGNAT) — to conserve IPv4 addresses and serve more customers than the number of public IPs they own.

Let’s break down the types of NAT and how ISPs use them:

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🧱 1. Standard NAT (on your router)

• This is what most home users have:

  • Your ISP gives your modem/router one public IP address.

  • Your router then uses private IPs (like 192.168.x.x) for your internal devices.

  • The router uses NAT to translate internal addresses to the public IP when communicating with the internet.

✅ This type of NAT is done on your equipment, not by the ISP — but it’s the foundation.

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🏢 2. Carrier-Grade NAT (CGNAT) – ISP-Level NAT

• When an ISP is short on public IPv4 addresses, it assigns customers private IPs from the special CGNAT range: 100.64.0.0/10.

• The ISP then uses NAT at its infrastructure level to map many customers onto a shared public IP.

💡 This means:

• Multiple customers share a single public IP address.

• Customers can still access the internet normally.

• However, it breaks port forwarding, hosting services, and some VPNs — unless the ISP uses workarounds.

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🚧 3. When ISPs Don't Use NAT

• If you're given a public static IP, your ISP doesn't need to use NAT — your IP is directly reachable.

• In business-class internet, NAT is less common; customers might get a subnet (e.g., /29) of public IPs.

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🔍 How to Tell If Your ISP Uses NAT (CGNAT)

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🧭 Summary

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So yes — many ISPs implement NAT, especially CGNAT, to deal with IPv4 shortages. If you want to avoid NAT, you typically need to request a public static IP (often for a fee).

Would you like help detecting whether your connection is behind CGNAT?

Yes, exactly — in Carrier-Grade NAT (CGNAT), the ISP provides the user with a private IP address (from a special CGNAT-reserved range), and internally maps that to a shared public IP address using NAT.

Here’s a detailed breakdown of how it works:

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📦 What You Get as a CGNAT User

• Your router or device is assigned a private IP address from this reserved range:

  100.64.0.0/10   →   100.64.0.0 – 100.127.255.255
  

• This range is not routable on the public internet, similar to 192.168.x.x or 10.x.x.x.

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🔁 What the ISP Does Internally

• The ISP has a NAT gateway (a large-scale NAT device) that maps:

  Your private CGNAT IP + Port  →  ISP’s public IP + Port
  

• This mapping is temporary and managed in a NAT table.

• The ISP can map thousands of customers to a single public IP using different port numbers.

Example:

So from the internet’s perspective, all users behind that public IP look like they come from 203.0.113.7, but on different ports.

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🚫 What You Can’t Do with CGNAT

• Host servers (web, game, mail) — incoming connections can’t reach you directly.

• Use port forwarding — since the public IP is not yours exclusively.

• Run certain VPNs, VoIP, or P2P apps without issues.

Some ISPs offer "port mapping" or "public IP on request" as a workaround — often for a fee.

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✅ How to Detect CGNAT

1. Check your device's IP address (on your router or PC) — if it's in 100.64.0.0/10, CGNAT is likely.

2. Compare with your public IP on https://ipinfo.io — if they’re different, NAT is involved.

3. Traceroute or run a WHOIS on the internal and public IPs — CGNAT addresses often don’t show external ownership.

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🧭 Summary

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Would you like a quick guide to check if you're behind CGNAT right now using command line tools or your router interface?