Mapping a MAC to an IP...

Chuck Anderson cra at WPI.EDU
Wed Jan 21 18:11:21 UTC 2009

On Wed, Jan 21, 2009 at 11:55:34AM -0600, Peter Laws wrote:
> Chuck Anderson wrote:
>> Put subnet-specific options in the subnet {}, and host-specific  
>> options in the host {}.  Do not put host {} inside subnet {}.  
> I get it now - we're using host to specify a reserved address which isn't 
> really host's function.

It depends.  If you mean to reserve a fixed-address for a client in a 
subnet, then you use a host statment (declared outside all subnet 
blocks).  fixed-addresses are handled separately in the server and do 
not follow the normal lease lifecycle nor are they stored in the 
dhcpd.leases file.  This is the traditional way to make sure a client 
gets a specific address all the time in the ISC dhcp server, and you 
must manually make sure any pool's range statements don't include the 
fixed-addresses in the range.

If you mean to reserve an address within a pool for a specific client, 
then you use a "reservation" in recent dhcpd releases.  Those are 
handled in the server like dynamic leases, follow the lease lifecycle, 
and are stored in dhcpd.leases.  You don't need to exclude these from 
the range, as they are dynamic leases.  How you declare a 
"reservation" or convert a regular dynamic lease to a "reserved" lease 
is outside my current knowledge :-)  It was a recent addition to ISC 

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