How to ConserveIPv4 AddressesWhile You Planfor IPv65 Ways non-technicalmanagers and networkengineers can worktogether to b...
1       KeeP DetAIleD ReCoRDs                                 Demand       You know how when it snows the bread and       ...
2             ConsolIDAte subnets                            Why do I lose addresses on each subnet?             Without g...
3                                                             4           ReClAIm ADDResses fRom                          ...
5           Get IP AlloCAtIons fRom                          Calculating your true utilization from           A sInGle PRo...
Get IPv4 allocations directly from ARIN                     summaryFor small organizations, you’ll have to go through a   ...
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How to Conserve IPv4 Addresses while You Plan for IPv6


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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 while You Plan for IPv6

  1. 1. How to ConserveIPv4 AddressesWhile You Planfor IPv65 Ways non-technicalmanagers and networkengineers can worktogether to better useIPv4 addresses beforethey run out Conserve sCarCe IPv4 resourCes We know, it sounds like a bunch of tree-hugging non- sense. But, the truth is that IPv4 addresses—the ones we’re currently using to connect to the Internet—are pretty much an endangered species. Lucky for us, IPv6 can provide an unimaginably large number of addresses. Not ready for IPv6 yet, you say? Then you’d better make like a treehugger and start using the IPv4 address space you already have more wisely. That will at least buy you some time to run IPv6 testing and develop an IPv6 implementation plan. This handy how-to guide offers five ways to get the most out of your existing IPv4 allocation. Share this information with your network engineers and use it to discuss the things they may already be doing to maximize your current IP space, and to begin evaluating your next steps for implementing IPv6. For more information on IPv6 and the things you should be doing to prepare your network, please visit ©2010 ZCorum. All rights reserved. Page 1
  2. 2. 1 KeeP DetAIleD ReCoRDs Demand You know how when it snows the bread and This is one area in which engineers could really use milk shelves at the grocery store are empty? some help from their non-technical managers.That’s poor demand planning and poor inventory Be sure you communicate with your network staffmanagement. so they understand how many new customers youSame goes for your network. You should be monitoring typically acquire in a given period, as well as how manyinventory, utilization and demand and keeping meticu- leave your service. If there are sales promotions cominglous records. up that may boost the normal number of customers acquired, be sure to give your technical team a heads- up. Knowing the net number of customer additions willInventory help them keep adequate addresses in inventory.Just like the grocery store, you need to know how manyaddresses you have in stock.You can keep your records up-to-date by reviewing yourIP inventory monthly. That’s sufficient for most indepen- Inventory you have Know how many addressesdent broadband providers; but, if you are adding many Utilizationnew customers each month or are approaching 85% assigned to Know which addresses are whether or equipment and users, andutilization of your IP allocation, you may need to review usedmore frequently. not they are really being Demand tomers you Know how many new cusUtilization typically acquire in a given time period, jects that may as well as any network proNow that you know how many addresses you have, you ignments, and require new address assneed to know how many are actually in use. plan accordinglyJust because your inventory list says an IP address isin-use doesn’t make it so. An IP logged “in-use” mayhave been given up when that equipment was removedfrom service, moved or upgraded, but your inventoryrecords might not have been updated.One way to determine utilization is to use ping tests ornetwork scanning tools. Just remember that these toolsgenerally can’t ping anything behind a router or firewall,so you may have to check those items manually.Copyright ©2010 ZCorum. All rights reserved. Page 2
  3. 3. 2 ConsolIDAte subnets Why do I lose addresses on each subnet? Without getting too technical, a subnet Every time you create a subnet, you lose three ad- is a logically visible subdivision of an IP dresses. Technically, you didn’t “lose” them, you justnetwork. For ISPs, the main benefit of subnetting is that can’t allocate them anywhere else because they have ait partitions your address space into a tree-like routing specific function to perform in the subnet.structure. The first address in the subnet serves and the networkThe downside to creating a whole bunch of subnets address. The last address in the subnet serves as theis that each one steals three addresses for its own use. broadcast address, so neither of these is a valid host forThat’s three addresses that you can’t allocate to paying end users. Another address in the subnet is also neededcustomers. to serve as the gateway or logical interface address. Why should I consolidate subnets? As IPv4 addresses become scarce—and as it gets harder to qualify for allocations from ARIN, which is already happening—you need to conserve your existing space and use it wisely. If you can roll several small subnets into a larger one, then you can recover three usable addresses for each subnet you eliminate. If you’ve got 8 subnets in one head end or central office and you can consolidate that into just 3 subnets, you can recover 15 addresses. Now apply that same theory to the rest of your head ends and central offices and we’re talking significant addresses recovered. That could give you enough IPv4 inventory to keep add- ing customers for a few more months while you finalize your IPv6 plans. You’re starting to see the benefits of being an IPv4-conservation tree-hugger now, right?Copyright ©2010 ZCorum. All rights reserved. Page 3
  4. 4. 3 4 ReClAIm ADDResses fRom lImIt stAtIC IP ADDResses ReseRveD Pools You’ve probably received requests from your Services that use PPP authentication, like customers for static IP addresses. In the spiritdial-up and some DSL networks, require reserved pools of good customer service, you’ve probably said “okay”.of IP addresses. Check the utilization and shrink these Stop that!pools accordingly. Why shouldn’t I give out static addresses?Drain the Dial-up Pool If you’re handing out static IP addresses, that address isBack in the day, you probably had an ocean (or at least no longer part of the pool you can share among otheran Olympic-size pool) full of reserved addresses to your dial-up services. That was okay becausethere were actually people swimming in it and making Residential customers don’t usually need a staticuse of those addresses. address. Unless they’re running a web server out of their home, that is.Fast forward to when you deployed broadband and themajority of those folks ditched dial-up. Did you drain But that would be a violation of your residential termssome of the water out of the “reserved for dial-up” IP of service, wouldn’t it?pool, or were you so focused on your new broadbandservice that you forgot? When should I give out a static address?Now’s the time to go take a look. If you’ve still got that Reserve a pool of static IP addresses for your businessOlympic-sized pool but only a handful of people are us- it, it’s time to down-grade to a kiddie pool. Reclaimas many addresses from that reserved pool as you can They may be running their own web servers or need aand move them into inventory for your broadband dedicated IP for remote access or secure In these cases, it is appropriate to assign a static IP address.Check Utilization on Other PoolsPerhaps you can move more addresses out as dial-upcustomers upgrade to broadband. You can reclaimwhatever is left when (or if ) you stop offering dial-up.If you’ve got other pools that aren’t being fully utilized,reclaim those addresses whenever possible.Remember to add your dial-up pool or any othersyou’ve created for dedicated purposes to the regularinventory check we suggested in the first section so youcan keep an eye on them.Copyright ©2010 ZCorum. All rights reserved. Page 4
  5. 5. 5 Get IP AlloCAtIons fRom Calculating your true utilization from A sInGle PRovIDeR multiple providers If you get an allocation from your backbone Now, let’s say you reach 85% utilization of the poolprovider and from your managed service provider from your managed service provider and ask for anor ARIN, you’ve got multiple inventories to manage. additional allocation.That’s eating up your time in tracking all those separate ARIN will look at all your available IP space to see ifallocations. you’re really at 85% utilization.Plus, having many sources for IP space may put you at You’ve got 256 addresses in your /24 from AT&T andrisk of getting your next IPv4 allocation request denied. 1280 addresses in your five “portable” /24s. Your totalWhy? available allocation is 1,536 addresses.Because ARIN requires that you be utilizing at least On average, you’re using about 1,088 addresses. That85% of your current allocation before you can justify puts your utilization at about 70%, not 85%.requesting a new one. So, you can’t get more any more space from yourAnd by current allocation, they mean all addresses to managed service provider or ARIN until you relinquishwhich you have access. the AT&T space you’re not using.Calculating your true allocation frommultiple providersLet’s say you have an AT&T backbone. AT&T probablygave you a /24 (256 addresses) as part of your servicepackage, even if you didn’t ask for it and don’t use it. How to apply for IP space from arIn If this is your first allocation request to ARIN, followYou also have a managed service provider that gives these steps:you five /24s (1280 addresses), which you use so 1. Review ARIN allocation policies in the Number Resource Policy Manual to confirmyou can change backbone providers—for optimal that you qualify for a direct allocation.bandwidth pricing, of course—and not have to re-IP 2. Get an Autonomous System Number (ASN),your whole network. You can just pick up this so-called create an ARIN web account, POC handle“portable IP space” and take it with you to the next and ORG ID.backbone provider. You use that allocation for all your 3. Complete and submit the forms for your initial IPv4 or IPv6 equipment and end users. 4. ARIN will evaluate your request and approveARIN will add your AT&T allocation and your “portable” it, or contact you for further information to determine eligibility.allocation to get your total current allocation. 5. Once the request is approved, pay the applicable fees and sign the Registration Services Agreement. Upon receipt, ARIN will notify you that your addresses are available for use.Copyright ©2010 ZCorum. All rights reserved. Page 5
  6. 6. Get IPv4 allocations directly from ARIN summaryFor small organizations, you’ll have to go through a You’re a card-carrying, IPv4-conserving tree-huggerthird party, such as your backbone or managed services now, aren’t you?provider, to request IPv4 allocations. But there’s no need to chain yourself to a rack of serversBut, if your network is large enough, you might be bet- to make a statement about your new-found passion forter off getting your IPV4 allocations directly from ARIN. IPv4 conservation.You can check the requirements for ISPs on Simply check in with your network engineers and share this handy how-to guide. Check off the techniquesGet IPv6 allocations directly from ARIN they’re already using:When you implement IPv6, ARIN prefers that ISPs • Keep Detailed Recordssubmit direct allocation requests. Check to • Consolidate Subnetslearn how you can qualify for direct IPv6 allocations. • Reclaim Addresses from Reserved Pools • Limit Static IP Addresses • Get IP Allocations from a Single Provider Then, find out what help or resources they need from you to implement additional techniques to use your existing IP space more efficiently. Once those engineers realize that you have a clue about IPv6 (if you don’t, read this IPv6 primer) and what it means for your network, they’ll be better able to help you figure out how to prepare for IPv6. And that’s good for everybody—you, your engineers, and your customers.Copyright ©2010 ZCorum. All rights reserved. Page 6