Client tied to pool via (sub)class in one subnet, same client has host declaration in other subnet...

Christian Marg marg at rz.tu-clausthal.de
Thu Sep 19 09:14:57 UTC 2013


Hello,

I've encountered a problem with our DHCP config:

A (mobile) client, having a host declaration with "fixed-address" in one 
subnet, gets it's IP, but the router IP etc. comes from another subnet - 
where that same client is bound to a pool via (sub)class.

The config looks like this:

====8<====8<====8<====8<====
subnet 192.168.65.0 netmask 255.255.255.0 {
   option domain-name "a.tu-clausthal.de";
   option routers 192.168.65.254;
   option domain-name-servers ...
   option broadcast-address 192.168.65.255;

   host a.a.tu-clausthal.de {
     hardware ethernet 5c:26:0a:06:11:2f;
     fixed-address 192.168.65.128; }
}

subnet 192.168.102.0 netmask 255.255.255.0 {
   option domain-name "b.tu-clausthal.de";
   option routers 192.168.102.254;
   option domain-name-servers ...;
   option broadcast-address 192.168.102.255;

   class "192.168.102-shared-pool"  {
	  match  hardware;
   }

   subclass "139.174.102-shared-pool-test" 1:5c:26:0a:06:11:2f;

   pool {
     failover peer	"dhcp";
     range		192.168.102.231 192.168.102.251;
     ping-check		true;
     max-lease-time	3600;
     min-lease-time	1800;
     adaptive-lease-time-threshold  80;
     allow members of	"192.168.102-shared-pool";
     deny dynamic bootp clients;
   }
}
====8<====8<====8<====8<====

Connecting it to a network port in subnet 192.168.65.0 leads to 
following result:

IP: 192.168.65.128
domain: "b.tu-clausthal.de"
router: 192.168.102.254
broadcast: 192.168.102.254

When I comment out the "subclass" line, it works as expected...

How can I work around this problem? I googled to see if I could the 
class match only if the giaddr is 192.168.102.254, but all I found was 
"that's not needed, DHCPD does that automatically" - which is usually 
right, but no solution to this problem...

Is there another way to restrict a Pool to certain MAC adresses?

Thanks in advance!

Best regards,

Christian Marg
-- 
Christian Marg                  mail  : mailto:marg at rz.tu-clausthal.de
Rechenzentrum TU Clausthal      web   : http://www.tu-clausthal.de
D-38678 Clausthal-Zellerfeld    fon   : 05323/72-2626
Germany                         jabber: ifcma at jabber.tu-clausthal.de


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