IPv4 smaller than /24 leasing?

Tue Mar 13 17:19:40 UTC 2018

On the consulting side, I do smaller than /24 blocks to customers over tunnels.  So far this is the only option we have found that works for the smaller ISP. We all know the routing table is bloated. We all know everyone *should* be moving toward IPV6.  A whole different discussion.  But, for now you have a subset of operators that are big enough to do BGP, maybe join an exchange, but not big enough to afford buying v4 space for each of their customers.  So they are utilizing a full /24 just to utilize it.  Things such as doing 1:many nat at each tower, doing Carrier Grade nat, and other things make it where they don’t necessarily need an IP per customer.  We all know that is ideal, but it’s not practical for the small to medium ISP.   Folks have brought up the argument that buying IPS is just the cost of doing business these days.  I argue that it isn’t.  I see networks with 2000 users and only a /24 running along very happy.  

I agree that the global routing table is pretty bloated as is.  But what kind of a solution for providers who need to participate in BGP but only need a /25? I can’t see going below that.

Justin Wilson
j2sw at mtin.net

www.mtin.net
www.midwest-ix.com

> On Mar 13, 2018, at 10:56 AM, Naslund, Steve <SNaslund at medline.com> wrote:
> 
> 
> Yes, exactly right.  You would probably have to tunnel the /27 back to where the >/24 lives.  That's the only way I can see of it working "anywhere".  That's a technically valid solution but maybe not so hot if you are looking for high redundancy/availability since you are dependent on the tunnel being up and working.
> 
> As always the reputation of the aggregate is going to be critical as to how well this works for you.  It seems to me that increasingly these "portable" blocks have murky histories as spam and malware sources.  I would rather have a block assigned by a reputable upstream provider than to do this.
> 
> Steven Naslund
> Chicago IL
> 
>> Le 2018-01-04 20:16, Job Snijders a Ã©critÂ :
>>> On Thu, 4 Jan 2018 at 20:13, Filip Hruska <fhr at fhrnet.eu> wrote:
>>> 
>>>> I have stumbled upon this site [1] which seems to offer /27 IPv4 
>>>> leasing.
>>>> They also claim "All of our IPv4 address space can be used on any 
>>>> network in any location."
>>>> 
>>>> I thought that the smallest prefix size one could get routed 
>>>> globally is /24?
>>> 
>>> 
>>> Yes
>>> 
>>> So how does this work?
>>>> 
>>> Probably with GRE, IPIP or OpenVPN tunnels.
>>> 
>>> Kind regards,
>>> 
>>> Job
>> 
>> IPv4 /24 is commonly the minimal chunk advertised to (and accepted by)
>> neighbors. If I run a global (or regional) network, I may advertise this
>> /24 -- or rather an aggregate covering it -- over my diverse
>> interconnection with neighbors, your /27 being part of the chunk and
>> routed to you internally (if you're va customer)-- no need for
>> encapsulation efforts. Similar scenario may be multi-upstream, subject
>> to acceptance of "punching holes in aggregates"... Am I missing
>> something? What's the trigger for doing tunneling here?
>> 
>> Happy New Year '18, by the way !
>> 
>> mh
>> 
> 
> 