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Re: IPv6 /48 advertisements
From: Edward Dore <edward.dore () freethought-internet co uk>
Date: Wed, 18 Dec 2013 22:47:37 +0000

Yes, from a filtering point of view a /48 in IPv6 is pretty similar to a /24 in IPv4, as perfectly illustrated by the 
two links in my post…

My point was that if you are getting the carrier to do the announcement for you then they can announce an aggregated 
/48 prefix and then break that up inside their network (if their internal policies allow it) to give the OP whatever 
prefix length per site they have decided on. The carrier only needs to carry the more specific prefixes on their 
backbone and the rest of the internet sees the aggregated prefix.

This all depends on the architecture of the OP’s network and what services they are buying from the carrier.

Of course, just getting a /48 per site and doing it properly would be the ideal scenario.

Edward Dore 
Freethought Internet 

On 18 Dec 2013, at 16:32, Blake Dunlap <ikiris () gmail com> wrote:

Regardless of the carriers, you'll find most ASs on the internet only listen to /48 or larger. So even if you get 
your prefixes accepted by your provider, don't assume you can get anywhere, or have your packets not fall in to uRPF 
blackholes randomly without a larger aggregate announcement.


On Wed, Dec 18, 2013 at 10:22 AM, Edward Dore <edward.dore () freethought-internet co uk> wrote:
If you’re talking about announcing each location separately, then RIPE have a couple of useful articles about prefix 
visibility on Ripe Labs:


Otherwise I guess you’ll need to talk to your chosen carrier(s) about aggregating your space for you, which will come 
down to their policies on what routes they will carry internally.

Edward Dore
Freethought Internet

On 18 Dec 2013, at 16:11, Cliff Bowles <cliff.bowles () apollogrp edu> wrote:

I accidentally sent this to nanog-request yesterday. I could use some feedback from anyone that can help, please.

Question: will carriers accept IPv6 advertisements smaller than /48?

Our org was approved a /36 based on number of locations. The bulk of those IPs will be in the data centers. As we 
were chopping up the address space, it was determined that the remote campus locations would be fine with a /60 per 
site. (16 networks of /64). There are usually less than 50 people at the majority of these locations and only about 
10 different functional VLANs (Voice, Data, Local Services, Wireless, Guest Wireless, etc...).

Now, there has been talk about putting an internet link in every campus rather than back hauling it all to the data 
centers via MPLS. However, if we do this, then would we need a /48 per campus? That is massively wasteful, at 
65,536 networks per location.  Is the /48 requirement set in stone? Will any carriers consider longer prefixes?

I know some people are always saying that the old mentality of conserving space needs to go away, but I was bitten 
by that IPv4 issue back in the day and have done a few VLSM network overhauls. I'd rather not massively allocate 
unless it's a requirement.

Thanks in advance.


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