IP address changing; any sendmail issues?

[Kenneth Porter]

kirsch at rge.com (Mathew Kirsch) wrote in <8hosg2$1f48$2 at info.rge.com>:

>Kenneth Porter <shiva at well.com> wrote:
>> My ISP has informed me that my IP address will be changing at the end
>> of the summer, due to a dispute between two address block holders (for
>> 170.1.0.0). They will be issuing me a new address soon. I expect that
>> I can deal with this by using both addresses on the interface
>> temporarily, then getting the DNS record changed, wait a week for the
>> old address to retire out of the DNS caches, then retiring the old
>> address. Anything I need to worry about wrt sendmail? (The primary use
>> of the box is as a mail hub.)
>
>As long as you are allowed to use both addresses during the transition
>period, and your ISP will route the IP addresses for the transition,
>there is no reason this shouldn't work reasonably well. It sure beats
>not having mail service at all until everyone's DNS updates.

It occurred to me that it might be tough for the ISP (RCN) to deploy the new 
addresses alongside the old, as all their routers would have to be told about 
this. I'm not sure just how capable the stuff is on their side. For example, my 
system is on SDSL, and the interface is in a /4 subnet, with only itself, the 
DSLAM, and the broadcast address sharing the subnet. If all commercial 
customers are set up that way, and many need to have public names, then quite a 
few routers are going to need temporary reconfiguration during the changeover.

Any idea how others deal with sudden IP address changes?