Mysterious missing DHCPv6 feature, was Re: How does one obtain an IPv6 DNS server when VPNing to an ASA?

[Ted Mittelstaedt]

On 5/27/2010 3:39 PM, Doug Barton wrote:
> On 5/27/2010 12:14 PM, Ted Mittelstaedt wrote:
>>
>> On 5/27/2010 6:53 AM, Gert Doering wrote:
>>> Hi,
>>>
>>> On Mon, May 24, 2010 at 12:42:30PM -0700, Doug Barton wrote:
>>>> I'm talking internal networks here. Lots of 1918 space available.
>>>
>>> I wonder why there's so much address collisions between VPN sites and
>>> at enterprise mergers and acquisitions...
>>>
>>
>> Because everyone uses 192.168.1.X since that's the default on
>> most translators.
>
> Right-O. Or 10.0.0.0/24, or what have you. At $SEVERAL_JOBS_AGO when we
> were talking about setting up subnets for an isolated internal project I
> suggested using 172.16/12 since we weren't using any of that space at
> the time, and I wanted the new thing to be clearly identifiable as
> "other." I was told that we couldn't do that because those were public
> addresses. Another time we were dealing with reorganizing some internal
> networks for local and remote offices I suggested that we _start_ our
> organizational plan at 10.200 and give each site their own /16. They
> looked at me like I had 3 heads.
>

We started assisting customers to put translators on their networks
about 10 years ago.  At that time I started with using 192.168.50.X
as I could see what was coming.  Since that time we have had 2-3 of
those customers interconnect either with other customers and that
has saved their bacon.  But much more than that - most customers 
nowadays have employees who VPN in, and those VPN's originate from
behind translators, almost always running 192.168.1 or 192.168.0,
and having the mothership NOT on the same subnet has helped 
troubleshooting immensely.

>> The solution - renumbering - isn't going to go away after IPv6.
>> When you have a merger you may get away with not immediately
>> renumbering as a result of IPv6 but you almost certainly are going
>> to be changing ISP's used at the acquired entity, and when you
>> do that you will have to renumber the inside network.
>
> ... or it's just easier to have everyone under the same prefix, etc.
> I've been on both sides of the M&A equation, so I think I understand the
> issues there pretty well.
>

same here.

> My point being that IPv6 doesn't magically fix the renumbering problems

Yes, we agree there.

> (such as they are) that exist in IPv4 today. It does make some things
> easier, but it comes at a cost. The important thing is to do a
> _realistic_ assessment of both the costs and the benefits.
>

realistic is a subjective and the weighing of costs and benefits is very
subjective.

Ted



>
> Doug
>