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List:       dhcp-server
Subject:    Re: Overlapping Leases with same hardware address
From:       Simon Hobson <shobson0309 () colony ! com>
Date:       2005-05-09 9:22:52
Message-ID: a06020404bea4da475f7d () [172 ! 20 ! 192 ! 95]
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Nico Rittner wrote:

>just detected the following duplicate,
>overlapping leases for the same
>hardware address.
>Can someone explain this behaviour ?
>Is this by design?

This really is a FAQ !

>lease 212.204.54.84 {
>     starts 1 2005/05/09 05:01:24;
>     ends 1 2005/05/09 10:01:24;
>     tstp 1 2005/05/09 10:01:24;
>     binding state active;
>     next binding state free;
>     hardware ethernet 00:11:5b:8e:bf:b7;
>     uid "\001\000\021[\216\277\267";
>     client-hostname "sven-029aqet31u";
>}
>
>lease 212.204.54.112 {
>     starts 1 2005/05/09 07:31:35;
>     ends 1 2005/05/09 12:31:35;
>     binding state active;
>     next binding state free;
>     hardware ethernet 00:11:5b:8e:bf:b7;
>     uid "\001RAS \000\021[\216\277\267\000\000\001\000\000\000";
>     client-hostname "sven-029aqet31u";
>}
>
>lease 212.204.52.122 {
>     starts 1 2005/05/09 07:31:35;
>     ends 1 2005/05/09 12:31:35;
>     binding state active;
>     next binding state free;
>     hardware ethernet 00:11:5b:8e:bf:b7;
>     uid "\001RAS \000\021[\216\277\267\000\000\000\000\000\000";
>     client-hostname "sven-029aqet31u";
>}

Apart from RTFM ...

The first leased addresses are different because the clients are 
different clients. Yes that is correct, they are different clients - 
as far as the DHCP server is concerned, the primary key (Client ID 
(uid in leases file)) is different, therefore it is a different 
client.

What's more, and this is also a FAQ, the second two are the windoze 
machines RAS service leasing (in this case) 2 addresses just in cases 
it might ever need to give one to a client, sometime, ever, perhaps 
never.

A search of the list archives will give you several ways to prevent 
leasing of addresses to RAS servers. I use :

if (substring (option dhcp-client-identifier, 1, 3) = "RAS") {
   ignore booting;
}


The same issue applies if you have a client that boots multiple OSs. 
Windoze always uses the MAC address as the UID, other OSs default to 
no UID and allow you to configure it if required.

Simon

-- 

NOTE: This is a throw-away email address which will reach me for as 
long as it stays spam-free, remove date for real address.

Simon Hobson MA MIEE, Technology Specialist
Colony Gift Corporation Limited
Lindal in Furness, Ulverston, Cumbria, LA12 0LD
Tel 01229 461100, Fax 01229 461101

Registered in England No. 1499611
Regd. Office : 100 New Bridge Street, London, EC4V 6JA.

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