migrate from (very) old dhcp/server to new one

Glenn Satchell Glenn.Satchell at uniq.com.au
Tue Aug 25 15:20:55 UTC 2009

>Date: Tue, 25 Aug 2009 13:48:36 +0200
>From: andreas.moroder at sb-brixen.it
>To: dhcp-users at lists.isc.org
>Subject: migrate from (very) old dhcp/server to new one
>we have a very old ( 3.0rc4 ) dhcpd Server on a SLES 8 and want to  
>migrate to a current version and a new server.
>Is there documentation available on how to do this and what are the pitfalls.
>Is it possible to migrate the actual dhcpd.leases file the way the  
>machines continue to get the same IP as they have now ?
>I discovered that for a reason I don't know for certain MAC addresses  
>there are more then one leases in the dhcpd.leases that have a past  
>"ends". Is there a tool to clean the file ? cleane_leases.pl does not  
>work because without -f it does not delete the decayed leases and with  
>-f it deletes leases it should not.
>Thank you very much

Hi Andreas

Wow! 3.0rc4 would be going back nearly 10 years now. Amazing for a piece
of software to run that long without an upgrade...

You can test your dhcpd.conf and dhcpd.leases files using the new
version of dhcpd, eg:

dhcpd -t -cf /path/to/dhcpd.conf -lf /path/to/dhcpd.leases
dhcpd -T -cf /path/to/dhcpd.conf -lf /path/to/dhcpd.leases

If you are not sure about the consistency of the current dhcpd.leases,
then I would suggest starting with a new empty dhcpd.leases file. Any
hosts with current leases will request a renewal of their existing IP
address. Many clients also remember their IP address and request it on
the next DHCPDISCOVER. Generally the clients will tend to retain the
old IP address.

Alternatively you can use your existing dhcpd.leases file if it passes
the tests above.

The other consideration is whether the new server will have the same IP
address as the old server. If this is the case then clients will find
it straight away and continue renewing their existing leases, otherwise
they will not get a response to their renewals and will eventually
time, out and go back to DHCPDISCOVER to find the new server.

This is a pretty easy conversion, and you should pick a suitable time
when tere will be some client activity so that you can test the new
server is  working properly. Even with no dhco server running, existing
clients will continue to work. Only new clients will fail to get an IP
address. I used to do dhcp server upgrades and restarts at lunchtime -
there was enough traffic to let you see that things were working,
rather than do it after business hours, and find there was a problem at
midnight when all the leases had expired :(

If anything is not clear please post more questions...

Glenn Satchell     mailto:glenn.satchell at uniq.com.au | I telephoned the
Uniq Advances Pty Ltd         http://www.uniq.com.au | swine flu info
PO Box 70 Paddington NSW Australia 2021              | line and all I got
tel:0409-458-580  tel:02-9380-6360  fax:02-9380-6416 | was crackling.

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