Option82 class matching problem

Oleg Gawriloff barzog at telecom.by
Tue Dec 30 15:27:33 UTC 2008

I'll have very simple setup:
L2 switch with Option82 activated
Cisco Router working as DHCP server (client interfacase on which relay 
is configures is, interface to dhcp server is
ISC DHCP server with address. Address is 
accessible from dhcp server.

ISC setup is:
use-host-decl-names on;
ddns-update-style none;
class "p2626-sha19/9"
    match if binary-to-ascii (10, 8, ".", option agent.circuit-id)="0.9";
    log(debug,"Class p2626-sha19/9 matched");
subnet netmask
{ }
subnet netmask
    option routers;
    pool { range; allow members of 
"p2626-sha19/9"; }

With empty dhcpd.leases file in log I see following:
[root at albatros2 /usr/local/src/dhcp-4.0.0]# dhcpd -cf 
/usr/local/etc/dhcpd.conf -lf /var/db/dhcpd/dhcpd.leases -d vlan0
Internet Systems Consortium DHCP Server V3.0.7
Copyright 2004-2008 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/
Wrote 0 leases to leases file.
Listening on BPF/vlan0/00:1e:0b:5a:d4:17/172.16.2/24
Sending on   BPF/vlan0/00:1e:0b:5a:d4:17/172.16.2/24
Sending on   Socket/fallback/fallback-net
DHCPDISCOVER from 00:17:08:47:54:34 via network 
10.254.254/24: no free leases
 Lease for Switch CID: 0.9 Switch RID:
Class p2626-sha19/9 matched
DHCPDISCOVER from 00:17:08:47:54:34 via
DHCPOFFER on to 00:17:08:47:54:34 (by171tobookhp) via
DHCPREQUEST for ( from 00:17:08:47:54:34 via lease unavailable.
DHCPNAK on to 00:17:08:47:54:34 via
 Lease for Switch CID: 0.9 Switch RID:
Class p2626-sha19/9 matched
DHCPREQUEST for ( from 00:17:08:47:54:34 
(by171tobookhp) via
DHCPACK on to 00:17:08:47:54:34 (by171tobookhp) via

I've really don't understand why its two DHCPDISCOVER (first one with 
'no free leases'), and why after successfull class matching there is 
'lease unavailable' error and DHCPNAK?
Last two entries at dhcpd.leases:
lease {
  starts 2 2008/12/30 14:14:02;
  ends 2 2008/12/30 14:14:09;
  tstp 2 2008/12/30 14:14:09;
  cltt 2 2008/12/30 14:14:02;
  binding state free;
  hardware ethernet 00:17:08:47:54:34;
  uid "\001\000\027\010GT4";
lease {
  starts 2 2008/12/30 14:14:18;
  ends 3 2008/12/31 02:14:18;
  cltt 2 2008/12/30 14:14:18;
  binding state active;
  next binding state free;
  hardware ethernet 00:17:08:47:54:34;
  uid "\001\000\027\010GT4";
  option agent.circuit-id 0:9;
  option agent.remote-id c0:a8:0:96;
  client-hostname "by171tobookhp";
Is someone can shed some light on this issue and point me to the right 

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