Failover and pools with single machines

Tina Siegenthaler tina at
Thu Dec 14 14:23:35 UTC 2006

Hi list

We have configured our dhcp server with lots of classes/subclasses/ 
pools that contain but one single host. The reason was that using  
"fixed-address" for assigning fixed addresses to hosts doesn't make  
those hosts appear in the lease file.
Now we'd like to implement failover... but what will happen to those  
pools with just one host? It's difficult to split a range of just one  
IP equally between two dhcp servers, and that's what failover does,  
if I understand it correctly. Can we use failover nevertheless, or  
will we run into problems? What happens when one server goes down?

Example config:

ddns-update-style none;
option domain-name-servers,;
option domain-name "";
log-facility local1;

# hosts
host PBG4 { hardware ethernet 00:0a:95:e6:xx:yy; }
host CODEC { hardware ethernet 00:50:60:80:xx:yy; }

# classes
class "PBG4" { match pick-first-value (option dhcp-client-identifier,  
hardware); }
class "CODEC" { match pick-first-value (option dhcp-client- 
identifier, hardware); }

# subclasses
subclass "PBG4" 1:0:0a:95:e6:xx:yy;
subclass "CODEC" 1:0:50:60:80:xx:yy;

# subnet 225, lower part
subnet netmask {
         option routers;
         option broadcast-address;
	pool { allow members of "PBG4"; range; }
	pool { allow members of "CODEC"; range; }
         pool {
                 allow unknown-clients;
         max-lease-time 21600;

Thanks for your help,


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