RE: Using /126 for IPv6 router links

["Matt Addison" <maddison () lightbound net>]

> From: Mathias Seiler [mailto:mathias.seiler () mironet ch]
> Subject: Re: Using /126 for IPv6 router links
>
> Ok let's summarize:
>
> /64:
> +     Sticks to the way IPv6 was designed (64 bits host part)
> +     Probability of renumbering very low
> +     simpler for ACLs and the like
> +     rDNS on a bit boundary
>
> <>    You can give your peers funny names, like 2001:db8::dead:beef ;)
>
> -     Prone to attacks (scans, router CPU load)
> -     "Waste" of addresses
> -     Peer address needs to be known, impossible to guess with 2^64
> addresses
>
>
> /126
> +     Only 4 addresses possible (memorable, not so error-prone at
> configuration-time and while debugging)
> +     Not prone to scan-like attacks
>
> -     Not on a bit boundary, so more complicated for ACLs and ...
> -     ... rDNS
> -     Perhaps need to renumber into /64 some time.
> -     No 64 bits for hosts

You're forgetting Matthew Petach's suggestion- reserve/assign a /64 for
each PtP link, but only configure the first /126 (or whatever /126 you
need to get an amusing peer address) on the link. 

+       Sticks to the way IPv6 was designed (64 bits host part- even if
it isn't all configured)
+       Probability of renumbering very low
+       simpler for ACLs and the like
+       rDNS on a bit boundary
+       Only 4 addresses possible (memorable, not so error-prone at
configuration-time and while debugging)
+       Not prone to scan-like attacks
+       Easy to renumber into a /64 if you need to

-       "Waste" of addresses

Seems to be a fairly good compromise, unless there's something I missed.

~Matt