Re: [DNA] Question regarding prefix assignment

[JinHyeock Choi <jinchoe@gmail.com>]

Dear Tero

> During the yesterday meeting it was brought up that using prefixes to
> conclude whether a link has changed or not can be problematic in certain
> cases. Can someone confirm whether the following scenario is possible or
> not?
> 
>                Router(s) advertising
>                  prefixes A and B
>                         |
>                         |__________X_______ AP2
>                         |                  (may use only prefix A)
>                         |
>                         |
>                        AP1
>               (may use prefixes A and B)
> 
> X marks a box-in-the-middle e.g. a bridge (as mentioned yesterday).
> 
> If this is possible, the problem lies here in the fact that if the node
> is first connected to the AP1 it can configure either prefix A or B, and
> if it then moves to AP2 it may only use prefix A even though still
> connected to the same link. Let's assume that a node uses prefix B and
> is connected to AP1. It also knows that the complete prefix list for the
> current link is A and B. It then moves to AP2 and receives an RA,
> notices that the advertised prefix(es) match and thus link has not
> changed. However, it's now using prefix B which is not valid under this
> section of the link.

Let me clarify the above

When the routers send an RA advertising both A & B, the RA 
will be forwarded both through AP1 and AP2. Right?

If so, that means that AP2 advertise the prefix B which is not 
supported in that (L2) link. I don't think that is valid. 

Best Regards

JinHyeock