[arin-ppml] ARIN-prop-167 Removal of Renumbering Requirement for Small Multihomers

Kevin Blumberg kevinb at thewire.ca
Thu May 3 00:48:08 EDT 2012


In practice your description of renumbering is completely valid. I have found that there are always edge cases
that complicate the situation. I had to renumber a /23 a couple years back that was supporting 1000 domains
for webhosting. I used a similar method you described below and that handled 85 percent of the customers.
Then the edge cases started cropping up, domains that we were not authoritative on, and the customer had
hard coded the A records for the old IP netblock. Customers that had hard coded the IP inside of scripts and firewalls. 
We spent countless hours contacting the customers to complete the work and every time we had to tip toe 
because we were inconveniencing them.  

I consider the initial decision to  renumber out of PA space and get your first PI space hard enough. It is a careful
balance of having freedom and flexibility with the work to renumber. To require  an organization to do it over and 
over again as they grow is wrong.

Kevin Blumberg

> -----Original Message-----
> From: arin-ppml-bounces at arin.net [mailto:arin-ppml-bounces at arin.net] On
> Behalf Of Jimmy Hess
> Sent: Thursday, May 03, 2012 12:12 AM
> To: Jo Rhett
> Cc: arin-ppml at arin.net
> Subject: Re: [arin-ppml] ARIN-prop-167 Removal of Renumbering
> Requirement for Small Multihomers
> 'On 5/1/12, Jo Rhett <jrhett at netconsonance.com> wrote:
> > On May 1, 2012, at 9:52 AM, William Herrin wrote:
> >> First there's DNS pinning. Because of DNS pinning, web browsers won't
> >> follow your new IP address when the DNS TTL runs out. In some cases,
> What?  Web servers are a snap to renumber; DNS pinning is not an
> issue.     Recursive DNS servers are harder to renumber,  because the
> IP addresses are often configured directly by hand  on end user systems,
> which means that a  per-system cost must be incurred  if this activity cannot
> be automated,  IT staff time must be consumed to
> reconfigure DNS server settings on each network device,   costs are
> incurred to the END user of the ISP,  and they may be  annoyed that their
> ISP's  renumbering  requires that they expend  man hours to update
> configurations of their equipment.
> Unfortunately, the DNS RFCs don't provide a method for a  recursive
> DNS server to tell the end user client system to   permanently
> reconfigure the IP address of the server queried to the new one (without
> end user intervention).
> A standard method of renumbering is to  transition services.
> Web servers get configured with both old and new IP addresses.
> The DNS records are updated, and both new and old IP addresses are valid
> until renumbering is completed.
> DNS pinning beyond a normal DNS TTL period would be an anomaly,  and
> is likely a unique issue to be addressed by the end user   (by
> rebooting their equipment).
> But beyond a few days, its an imaginary problem.
> Note that the ARIN /24 policy allows a 12 month transition period, which is
> plenty of time to have DNS changes to a webserver hostname take effect.
> Browser windows don't get left open for 3 months.    Even if the DNS
> pinning _DID_ happen to be broken in some version of a major browser
> in use by users;    that can be addressed by the amount of time  that
> the renumbering is performed over.
> It is not as if the /24 assignment policy requirement is that the ISP complete
> their renumbering  within 30 days.
> --
> -JH
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