IPv6 Default Allocation - What size allocation are you giving out

Thu Oct 9 20:49:01 UTC 2014

On Thu, Oct 9, 2014 at 4:32 PM, Roland Dobbins <rdobbins at arbor.net> wrote:
>
> On Oct 10, 2014, at 3:25 AM, Baldur Norddahl <baldur.norddahl at gmail.com> wrote:
>
>> I am sure there are. Tell me about them.
>
> This issue has been discussed on all the various operational lists many, many times over the years.
>
> <http://tools.ietf.org/html/rfc6752>

Hi Roland,

6752 isn't germane; it has to do with using private IP addresses on
routers, which borks things up when the router has to generate an ICMP
type 3. Baldur want's to know: why not just use one public IP address
per router and use it on all interfaces?

Baldur, one IP per router can work just as well as one subnet per
interface. But there are some gotchas:

Your router has one IP. Your customer has a subnet. Do you add an
extra deaggregated single IP to your routing table for his router?
There are more routers than links, so if you assign subnets to routers
instead of links you'll have to carry more routes.

If you borrow the customer LAN-side IP for the WAN side you'll get
grief when his equipment is one of those that doesn't respond if the
LAN-side interface is down (e.g. Cisco). That gets kind of nasty when
troubleshooting and remediating problems.

And of course the more knowledge you can gather from diagnostic tools
like traceroute, the more quickly you can identify the problem when
something doesn't work right..

In my own networks... I want to keep as many IPv4 addresses as I can,
so my router interfaces borrow their ip from loop0. In IPv6 where I
can have a functionally infinite number of /124's I want to put one on
each interface and gain the mild extra benefit.

Regards,
Bill Herrin

-- 
William Herrin ................ herrin at dirtside.com  bill at herrin.us
Owner, Dirtside Systems ......... Web: <http://www.dirtside.com/>
May I solve your unusual networking challenges?