How to Conserve IPv4 Addresses


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Five ways managers and network engineers at independent ISPs can work together to better use IPv4 addresses before they run out. These slides accompany our guide "How to Conserve IPv4 Addresses While You Plan for IPv6" available at

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How to Conserve IPv4 Addresses

  1. How to Conserve IPv4 Addresses While You Plan for IPv6
  2. Five ways non-technical managers and network engineers can work together to better use IPv4 addresses before they run out.
  3. Why Should I Conserve v4 Addresses? The End is Near IANA is out of IPv4 addresses. IPv6 will replace IPv4, but… You’re not ready, are you?
  4. What to do? Conserve the IPv4 space you have now, while you get ready for IPv6.
  5. Step #1 Keep Meticulous Records
  6. Inventory Know how many addresses you have. Utilization Know which addresses are assigned to equipment and users, and whether or not they are really being used. Demand Know how many new customers you typically acquire in a given time period, as well as any network projects that may require new address assignments, and plan accordingly.
  7. Step #2 Consolidate Subnets
  8. Each subnet claims 3 IP addresses: <ul><li>1 for the network address
  9. 1 for the broadcast address
  10. 1 for the gateway or logical interface address </li></ul>So, you have fewer addresses to allocate to paying customers. Consolidate unnecessary subnets and reclaim those addresses to use until you implement IPv6.
  11. Step #3 Reclaim Addresses
  12. Drain the Pools <ul><li>Check your old (dial-up) pools, reclaim what isn’t being used
  13. Shrink under-utilized pools
  14. Make sure all IP pools are being monitored for utilization </li></ul>
  15. Step #4 Get Rid of Static
  16. Who needs a static IP? Residential users? Not usually, unless they’re running a web server. But that’s a violation of your terms of service, isn’t it? Businesses customers? Possibly. If they’re running a web server or processing secure transactions, then yes.
  17. Step #5 Get a Single Provider
  18. Calculate your true allocation: <ul><li>How many IP addresses do you get from your backbone provider (even if you don’t use them)?
  19. How many do you get from ARIN or a managed services provider (think “portable” IP space)?
  20. Add ‘em all up. </li></ul>
  21. Calculate your true utilization: <ul><li>How many IP addresses are in-use in your network?
  22. Divide the in-use addresses by the total allocation you calculated in the previous slide to see true utilization.
  23. If utilization is 85% or greater, you may qualify for another IPv4 distribution. If not, consider surrendering the IP space from other providers and consolidate with one provider, then request additional IPv4 space through that provider. </li></ul>
  24. Download the full How-to Guide:
  25. Is Your Network Ready for IPv6? Get tested.