The second in a collection of blogs all through 2025 highlighting the state of IPv6 throughout the business, greatest practices to think about, and the way Cisco helps prospects on their journeys with its services.
IPv6 Is Right here to Keep
As we mentioned in our earlier publish, IPv6 has lastly arrived and is right here to remain, with all measurements and information shortly pointing in direction of an IPv6-dominant future. So, what do private and non-private sector organizations have to do to arrange for this variation that’s taking place proper underneath our toes? Clearly coaching and training will probably be vital for IT groups, and full stock will probably be wanted (what property and techniques are both prepared now, could be prepared through future software program replace, or will must be segmented off and/or refreshed over time). However an typically ignored, but highly effective, piece of the puzzle is the acquisition of IPv6 tackle area and its correct allocation.
Greedy the Scale of IPv6 Tackle House
It’s no secret that IPv6 has a bigger area, however simply how a lot bigger? We’ve moved from 32-bits to 128-bits, however how will we wrap our heads round that? How does 4.3 billion (4,294,967,296) evaluate to 340 undecillion (340,282,366,920,938,463,463,374,607,431,768,211,456)? An analogy I like to make use of is that this: if all 4.3 billion IPv4 addresses might slot in 1-inch (2.54 cm), then the IPv6 area would cowl twice the size of the observable universe. The numbers are actually astronomical! And it means we’re free of the burden of the constrained pondering that IPv4 introduced with it.
Transferring Past IPv4 Constraints
We beforehand cared about maximizing the effectivity of our tackle area, attempting to squeeze each final bit out of IPv4 allocation lest something go to waste. We launched applied sciences like VLSM, CIDR, and NAT (mixed with RFC 1918 non-public tackle area) to increase the lifetime of IPv4. (And it needs to be acknowledged these labored splendidly effectively – shopping for us not simply a few years, however a few many years). Nevertheless it’s time to desert this constraint mentality and embrace the liberty that 2128 offers.
Rethinking Subnets
We not must depend the variety of hosts on our subnets – we are going to use a /64 prefix for each user-facing subnet. Half of our 128-bit tackle will signify the prefix (or “subnet” or “community” as these are sometimes used interchangeably), and half will signify the interface identifier (generally known as a “host ID”). This may increasingly appear extremely wasteful, however it’s how the protocol was designed. And as RFC 7421 highlights, many issues begin to break should you diverge from /64 boundary. So, whether or not you will have 2 nodes, or 2 trillion (!) nodes on a single /64 subnet, 99.99+% of the addresses area on that subnet will go unused. And whereas surprising to listen to at first, it’s fairly liberating as soon as accepted.
We’re not underneath the onus of counting (or predicting) the variety of hosts anticipated to reside on every subnet, and attempting to measurement appropriately: not making the subnet too small and being unable to suit all of the hosts, but additionally not making it too large when these potential addresses could possibly be used elsewhere within the community. Now, all subnets will use a /64.
So what number of of those /64 subnets are wanted? Once more, throw away the IPv4 mentality of counting complete numbers. We are able to use the plentiful tackle area to create an IPv6 addressing plan that can look considerably completely different out of your IPv4 one. In case you are a company of any respectable measurement, go to your RIR (Regional Web Registry) – ARIN, RIPE NCC, APNIC, AFRINIC or LACNIC – and get an IPv6 allocation that’s a lot bigger than you suppose you may want. It’s now customary for enterprises to obtain between a /29 and a /32, which give about 4 billion to 32 billion /64 subnets inside them, respectively. That is an thrilling change from the insurance policies of 10+ years in the past!
Benefits of Giant IPv6 Allocations
Whereas this can be very unlikely that you’ll use billions of subnets, these massive allocations present the flexibleness to start out eager about a hierarchical addressing plan, the place every layer within the hierarchy takes on some significance referring to both possession (campus/department vs. cloud infrastructure vs. colocation facility), geography, practical/logical place within the community, or plain subnet numbering (which could be mapped 1:1 to VLANs). Moreover, and really excitingly, every layer could be aligned with one nibble, that’s, 4 bits, or one hexadecimal character.
So moderately than having an inconsistent mess of subnets, all of various sizes and fragmented throughout your entire community, we will now obtain consistency and ease whereas additionally having the ability to embed semantic that means within the tackle itself – nice for each troubleshooting and basic operations and one thing that was almost unimaginable in IPv4. This could then additionally result in cleaner and easier routing tables and ACLs – a profit for each your networking and safety groups.
Embrace the IPv6 Alternative
Use this transition to IPv6 as a possibility to start out recent and free yourselves from the shackles of IPv4 constraint. Get a big allocation out of your RIR and begin planning for a greater (addressed) future as we speak!
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