Re: [nznog] BCP / Guidance on IPv6 prefix size to provide to customers

I also believed a valid argument at the same time is that if a customer is legitimately using an entire /48-56 (I’d say its somewhere within this range - Open to debate on this.) and is requesting more, perhaps you should be redirecting them to APNIC to apply for their own PI address space. From a growth perspective it makes sense for the customer, however at the same time it doesn’t give you quite so much vendor lock into your services. Obviously the flip side of this is if they refuse to get PI Addressing you should of course allocate them appropriate addressing. At the end of the day I see this as the right approach because I want large customers to design their network right regardless of vendor providing the services. Cheers, Fraser

On 3/01/2015, at 7:59 am, Brian E Carpenter wrote:

On 02/01/2015 20:56, Jeremy Visser wrote:

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On 2 Jan 2015, at 08:22, Ben wrote:

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The general recommendation seems to be to give out /48s to users. Although you may only have a /32 at the moment, you can apply for more space in the future if you require it.

It is generally given that /48 is the smallest allocation that one can advertise over the internet. And if a customer wants to multihome in multiple locations then each location should have a /48 at the least.

The latter isn’t a valid reason for the former, as space assigned to customers by ISPs is by definition non-portable.

There was an argument, which I think was in (obsolete) RFC 3177, that if all providers hand out the same length prefix, customers would never have to redesign their site addressing plan if they switched providers and had to accept a longer prefix. The more recent recommendation is that site numbering plans should simply number subnets compactly rather than sparsely, to avoid needing a short prefix when it isn't strictly necessary.

All the same, handing out /56s means assuming that your customers never need 257 subnets. That may sound like a lot, but think about possibilities such as large numbers of virtual subnets.

Brian

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Not arguing against /48’s or anything, though.

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