The second in a sequence of blogs all through 2025 highlighting the state of IPv6 throughout the trade, finest 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 put up, IPv6 has lastly arrived and is right here to remain, with all measurements and knowledge shortly pointing in the 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 occurring proper beneath our toes? Clearly coaching and schooling might be mandatory for IT groups, and full stock might be wanted (what property and programs are both prepared now, will be prepared by way of future software program replace, or will have to be segmented off and/or refreshed over time). However an usually missed, but highly effective, piece of the puzzle is the acquisition of IPv6 handle area and its correct allocation.
Greedy the Scale of IPv6 Deal with Area
It’s no secret that IPv6 has a bigger area, however simply how a lot bigger? Now we have moved from 32-bits to 128-bits, however how can we wrap our heads round that? How does 4.3 billion (4,294,967,296) examine 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 may 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 considering that IPv4 introduced with it.
Shifting Past IPv4 Constraints
We beforehand cared about maximizing the effectivity of our handle area, making an attempt 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 handle area) to increase the lifetime of IPv4. (And it ought to be acknowledged these labored splendidly properly – shopping for us not simply a few years, however a few a long time). But it surely’s time to desert this constraint mentality and embrace the liberty that 2128 supplies.
Rethinking Subnets
We now not should depend the variety of hosts on our subnets – we’ll use a /64 prefix for each user-facing subnet. Half of our 128-bit handle will symbolize the prefix (or “subnet” or “community” as these are sometimes used interchangeably), and half will symbolize the interface identifier (typically 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 in the event you diverge from /64 boundary. So, whether or not you’ve got 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 stunning to listen to at first, it’s fairly releasing as soon as accepted.
We’re now not beneath the onus of counting (or predicting) the variety of hosts anticipated to reside on every subnet, and making an attempt to dimension appropriately: not making the subnet too small and being unable to suit all of the hosts, but additionally not making it too huge when these potential addresses might 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 whole numbers. We are able to use the plentiful handle area to create an IPv6 addressing plan that may look considerably totally different out of your IPv4 one. In case you are a corporation of any first rate dimension, 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 would possibly 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 pliability to begin desirous about a hierarchical addressing plan, the place every layer within the hierarchy takes on some significance regarding both possession (campus/department vs. cloud infrastructure vs. colocation facility), geography, practical/logical place within the community, or plain subnet numbering (which will be mapped 1:1 to VLANs). Moreover, and really excitingly, every layer will be aligned with one nibble, that’s, 4 bits, or one hexadecimal character.
So somewhat than having an inconsistent mess of subnets, all of various sizes and fragmented throughout your complete community, we are able to now obtain consistency and ease whereas additionally with the ability to embed semantic that means within the handle itself – nice for each troubleshooting and common operations and one thing that was practically unattainable 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 begin 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 right now!
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