[ipv6-wg] IPv6 on P2P links

I would say it depends on which type of point-to-point links you are looking at.

I used to be involved in a larger PPP-based DSL network, which only ran on Link-Local for the PPP links. Routing wise there wasn't much to go wrong there with the client having a default route pointing to the PPP link, which acts as a tunnel. From the central hub's perspective the only thing you need is a single static route (might be inserted via AAA) to the client side of the PPP.

The only real caveats in this case are the fact the receiving end must be a bit of a weak host and at least capable of sourcing ICMP messages from another interface to make sure they are routed to the destination and not dropped because of scope rules. The great benefit is that is saves you the headache of keeping track of 2 IPv6 pools and the additional logging/reporting you may need to satisfy your local LEAs.

In the core of the network it does make sense to run Global Unicast addresses on every interface. It makes troubleshooting much easier if you actually see ICMP coming from the correct interface instead of a central loopback address. The same might be the case for routing, having it point to a traceable address will probably make your life  just that little bit more enjoyable.

The one thing you have to keep in mind when you assign GUAs to your point-to-point. Is that while it make sense to assign  /127 (or /126 as some people seem to insist on doing), it might be wise to always reserve the full /64 for that link. While most major vendors these days support /127 or are under a lot of pressure to do so, some still believe in rfc 3627 and follow it to the letter. I also came across people who stopped reading half way just after the part where the rfc says everything must be 64 bits. So while your current choice of vendor allows you to run smaller subnets, be prepared that somebody else isn't. You might be forced to switch back to /64 at some point in time after switching to another brand or some remote peer might not be able to be compliant. Having the /64 ready there might save you time and it also allows to put your links in easy to remember addresses.

Grtx,

MarcoH

On May 26, 2011, at 10:07 AM, Jasper Jans wrote:

> Can anyone give me some real world experience with IPv6 numbering on P2P links in their network?
> 
> I've seen the recommendations swing from '/64' to '/127 if your equipment can handle it' and even
> to 'do not assign anything at all just use link-local' and access your devices over the loopback
> which your IGP will distribute.
> 
> The last option seems interesting to me from a IP assignment point of few. It safes me having
> to allocate a block for this part of the infrastructure. I'm just wondering if in the long run
> it will not make life harder.
> 
> Jasper
> 
> 
> Op dit e-mailbericht is een disclaimer van toepassing, welke te vinden is op http://www.espritxb.nl/disclaimer
> 
>