While I agree with the general sentiment that the IP change and switch change will likely be smooth, the IP change can be done more transparently and has literally nothing to do with the L2 gear.
To that end, I don't see any reason to not configure/assign the new IP block now and let folks start using it right away, even before the switch switch.




On Tue, 2012-08-21 at 15:54 -0700, Owen DeLong wrote: 
On Aug 21, 2012, at 14:07 , Doug McIntyre <merlyn@IPHOUSE.NET> wrote:

> On Tue, Aug 21, 2012 at 03:54:19PM -0500, Jay Hanke wrote:
>> On Tue, Aug 21, 2012 at 3:46 PM, Mike Bushard, Jr
>> <mike.bushard@arvig.com> wrote:
>>> I typically would agree Owen, but in this case it may make sense. Everyone
>>> will be down already, and we won't have multiple outages to the entire
>>> exchange for IP changes. There will be a considerable amount of work if
>>> everyone changes addressing on different schedules. I think just saying
>>> that on day x we are on the long term strategy will save time in this
>>> case. Our topology is pretty basic today so I think the rick would be
>>> minimal at this time.
>>
>> The time frame is pretty tight for everyone to coordinate bilateral
>> changes. Esp for the bigger folks.
>>
>> What about enabling the new IP addresses on the existing topology and
>> moving one of the route servers to the new block. Then setting a flag
>> date to remove the existing IP addresses 2 months out.
>
>
> I'm sorry I've been so under the weather, that I've been behind and
> haven't started coordinating the renumbering with my co-conspirators.
>
> Jay, one problem with a method like that, is that there isn't a
> central router.  Everybody is talking all in the same flat space. If
> somebody changes to talk on their 206.108.255.0/24 IP address, then
> those that haven't changed yet won't know how to reach their routes.
> Thus breaking the exchange apart into those that have adjusted, and
> those that haven't adjusted. What more, the unconfigured people will
> see the new routes, but can't reach them.
>
There's no reason people can't add the new addresses and migrate
peering sessions individually, one peer at a time, then remove the
old addresses once that's complete.

I think two months would be a bit narrow on the time frame, however.

>
> What follows is the plan I had in my head (but not communicated yet)
> until I saw the oppertunity to just do it all at once.
>
> We communicate everybody's new 206.108.255.0/24 IP & 2001:504:27::/48
> address, which almost certainly will just be reusing the same last
> octet as the current one.
>

Might I suggest on the IPv6 block 2001:504:27:0::/64 be used for the
exchange (we can use other parts of the /48 later if needed) and that
we number as follows:
	2001:504:27:0:AS:NO:XXXX:YYYY

Where AS:NO is the 32 bit as number and XXXX:YYYY is a number chosen
by the applicable AS to represent the specific router/port combination.
(Yes, 32 bits for router/port combinations is overkill, but I can't think of
a better use for the bits).

> Everybody does a secondary of these IP addresses on their MICE facing
> interface. This has to be completed by such-and-such date. We'd do
> spot checks with ping to make sure people have completed this.
>

I would actually suggest making the existing address "secondary" and
the new addresses "primary" to reduce future downtime.

> Meanwhile, we build duplicate BGP sessions in the route reflectors for
> when people are ready to cut.
>

+1

> After the such-and-such date, then people are free to cut over their
> BGP sessions to originate from their new IP, and connect to the new
> BGP session on the route reflectors.
>

I think the RS peering sessions can be cut this way, but suggest you
look over my earlier proposal for managing the peer to peer sessions.

> Finally, there is a drop-dead date when all use of the old IP ranges are done.
>
> This way, when somebody cuts onto the new BGP session, the
> unconfigured old people still have a way to reach the new routes
> (via. the secondary IP addresses configured on their interface). But
> their BGP sessions don't change until they want them to.
>

An excellent solution for the RS peering sessions.

> This way is slow, and requires 100% compliance in getting the
> interface secondary addresses, and then in the final drop-dead date.
>

Actually, it doesn't require 100% compliance. People can actually add
the interface secondaries at their convenience and everything continues
to work with their old address until they choose to cut over.

> OOTH, if everybody goes down for the switch cut, then people can bring
> up their session when they want to after the maintenance window, but
> that also means everybody has to be available to cut their configs
> over that night/weekend as well if they want to continue to talk on
> the exchange.

If everyone were only peered with the RS, I'd say this might be a feasible
approach. However, since they aren't, I'd suggest that we point out the
switch cut as a "recommended time" to apply the new addressing to their
interfaces and leave it at that.

Owen

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