Cleanup leases?

Simon Hobson dhcp1 at
Thu Sep 28 18:35:09 UTC 2006

Jeff A. Earickson wrote:

>And we use
>to backup our Mac office clients.  Retrospect really (stupidly!)
>expects IP numbers not to change for backup clients.

No it doesn't.

>   Since we
>don't want to use static/bootp addresses for hundreds of Mac
>clients, a long lease time is in our favor.  We consider Retrospect's
>keying in on IP numbers to be a defect in their product, BTW.

It isn't a defect as it has no such limitation UNLESS YOU CONFIGURE 
IT THAT WAY. In other words, you CAN make it a pain, but it isn't the 

I have a good idea what the problem is - you are doing backups across 
subnets, and have disabled directed broadcasts in the routers. This 
means that Retrospect cannot broadcast to find clients that aren't on 
the local subnet and so you have to add them by IP address - at which 
point it DOES require the client to stay at that address.

Try a Google search for "retrospect broadcast subnet", in particular 
this article caught my eye :

What this guy has done is to tell Retrospect that there is a subnet 
at a.b.c.d/ where a.b.c.d is the IP address of the 
client. This means that Retrospect will broadcast to a.b.c.d to find 
any clients on the subnet - and of course in this case there can be 
only one. Because as a network packet, this broadcast is not really a 
broadcast, the routers allow it through.

If the client changes, all the admin has to do is add a broadcast 
subnet for the new address and the client will be found. The 
alternative of adding by IP address means removing the client from 
the server config ("Forget client" in Retrospect terminology) and 
adding it in again - that IS a right royal PITA.

This workaround isn't a proper answer, but it will make things work 
until you get the router configs fixed - enable directed broadcasts.

Now your network admins will probably scream at you and absolutely 
refuse to support satanistic features such as directed broadcasts. If 
they do then give them that pitying look and simply ask if they 
haven't heard of access control lists ? And would they like mummy or 
daddy to show them ?

OK, that's perhaps a bit too far, but I think you get the idea ! They 
may not want to allow directed broadcasts (it's a good way of making 
lots of network traffic remotely), but they should be able to allow 
it from your backup server(s) or admin subnet. This is all that 
Retrospect needs in order to work across subnets and NOT find clients 
by IP address.

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