Dynamic and static leases present

Brian Raaen braaen at zcorum.com
Thu May 15 19:32:57 UTC 2008

Dear Todd,
	My understanding is even if you have a static assignment you will need for 
that address to not be included in the "range" or other dynamic clients will 
get the address.  I have duplicated and confirmed this behavior.  ISC dhcpd 
will do this unlike Microsoft Windows dhcp that has the concept 
of 'reservations'.  Our company tends to reserve the top or bottom part of a 
subnet to not be in a range when we want to assign static addresses.  Just 
make sure that the ip in question is not in the range and you will not have 
this problem.  One way to think of things is that a range in a "pool" of 
addresses that the server can assign to anyone, setting the host entry 
basically tells the server that if I can not have that address I will not 
have one at all.  If the address has already been taken it will just sit 
there and not accept any other offer.

Brian Raaen
Network Engineer
braaen at zcorum.com

On Thursday 15 May 2008, Todd Snyder wrote:
> I have my subnets defined as discussed the other day:
> subnet netmask { range
>; option routers; }
> And I have a host entry for the middle of the range:
> host ns03 {    
> 	hardware ethernet 00:1a:64:8a:62:42;    
> 	option host-name "ns03";    
> 	fixed-address; 
> } 
> But when the device tries to get an ip, I get the following in my logs:
> May 15 18:49:02 sa-bmp01 dhcpd: Dynamic and static leases present for
> May 15 18:49:02 sa-bmp01 dhcpd: Remove host declaration ns03 or remove
> May 15 18:49:02 sa-bmp01 dhcpd: from the dynamic address pool for
> 172.25.106/24 
> One page I read suggests that I can't have a static assignment in the
> middle of a dynamic range, but I don't believe that to be correct.
> My understanding is that I can assign a static ip within a dynamic
> range, and it's basically 'reserved' until that mac address asks for an
> IP, which it is then given from it's host declaration.
> Can anyone identify the error, or clarify whats going on here?  My brain
> isn't working with me on this one ....
> Thanks,
> Todd.
> ...................................
> Todd Snyder
> Tools Analyst
> Blackberry Operations
> Research In Motion Ltd.
> 519-888-7465 x73176
> tsnyder at rim.com 
> ...................................
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