migration suggestions

Daniel J McDonald dan.mcdonald at austinenergy.com
Thu Aug 20 12:21:51 UTC 2009

On Wed, 2009-08-19 at 08:22 -0500, Terry L. Inzauro wrote:
> sthaug at nethelp.no wrote:
> >>> If your clients can live with some downtime (remember, this will only
> >>> affect *new* clients which don't already have a lease), you can shut
> >>> down everything and move it all in one go.

Because of how long it will take to update all of the helper-addresses,
I don't think that would be viable.  If it were just a few dozen
networks, it might be possible, but hundreds will take a couple of
hours.  Working alone, I figure I can do 2 routers per minute, assuming
no distractions, so it is possible I might get it all done in under an
hour, but not likely.

> >> wouldn't that cause IP conflicts, as the new infrastructure wouldn't
> >> know the old leases?
> > 
> > Um, I had assumed that you would copy over the leases files - otherwise
> > you will indeed have problems as you suggested.
> > 

> If I may ask, why are you moving machines? If I were a gambling man, I'd say it was to re-purpose some hardware or something
> along those lines.  If that is the case, virtualization can be your good friend in a time of need.

We had collocated DNS and DHCP.  I'm moving DNS to anycast with load
balancers (Cisco ACE), and moving DHCP off the DNS servers seems a whole
lot easier than trying to come up with a way to load-balance DHCP over 6
servers in an anycast topology.  That and changing DNS server addresses
on thousands of hard-coded systems (in addition to the thousands that
get the addresses via DHCP) would be nightmarish.

Daniel J McDonald, CCIE # 2495, CISSP # 78281, CNX

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