DHCPDISCOVER coming in on server's native interface

[Oscar Ricardo Silva]

We have a RHEL 5.3 server running isc 3.1.1  in a Cisco environment 
where the dhcp server's address is set as the ip helper on the routing 
interface.  This setup works fine and clients on different networks are 
able to get addresses, etc.  Normally, DHCP traffic is seen as coming in 
via the router's address for that particular network:

Oct 29 10:24:02 DHCPSRV dhcpd: DHCPDISCOVER from 00:25:00:43:94:cc via 
192.168.14.1
Oct 29 10:24:02 DHCPSRV dhcpd: DHCPOFFER on 192.168.15.123 to 
00:25:00:43:94:cc via 192.168.14.1
Oct 29 10:24:03 DHCPSRV dhcpd: DHCPREQUEST for 192.168.13.208 
(172.16.200.34) from 00:26:4a:19:7b:40 (Macintosh-10) via 192.168.11.1
Oct 29 10:24:03 DHCPSRV dhcpd: DHCPACK on 192.168.13.208 to 
00:26:4a:19:7b:40 (Macintosh-10) via 192.168.11.1
Oct 29 10:24:03 DHCPSRV dhcpd: DHCPREQUEST for 192.168.58.228 
(172.16.200.34) from 00:25:4b:c7:10:c2 via 192.168.53.1
Oct 29 10:24:03 DHCPSRV dhcpd: DHCPACK on 192.168.58.228 to 
00:25:4b:c7:10:c2 via 192.168.53.1
Oct 29 10:24:07 DHCPSRV dhcpd: DHCPDISCOVER from 00:26:4a:17:77:2e via 
192.168.35.1
Oct 29 10:24:08 DHCPSRV dhcpd: DHCPOFFER on 192.168.35.107 to 
00:26:4a:17:77:2e via 192.168.35.1
Oct 29 10:24:09 DHCPSRV dhcpd: DHCPREQUEST for 192.168.35.107 
(172.16.200.34) from 00:26:4a:17:77:2e via 192.168.35.1
Oct 29 10:24:09 DHCPSRV dhcpd: DHCPACK on 192.168.35.107 to 
00:26:4a:17:77:2e via 192.168.35.1



The server is addressed at 172.16.200.34 (network 172.16.200.32/27) on 
eth0.  We're seeing some client requests coming in from "eth0"

Oct 27 23:42:57 DHCPSRV dhcpd: DHCPDISCOVER from 00:22:15:0d:e7:96 via 
eth0: network 172.16.200.32/27: no free leases
Oct 27 23:43:29 DHCPSRV dhcpd: DHCPDISCOVER from 00:22:15:0d:e7:96 via 
eth0: network 172.16.200.32/27: no free leases
Oct 27 23:43:33 DHCPSRV dhcpd: DHCPDISCOVER from 00:22:15:0d:e7:96 via 
eth0: network 172.16.200.32/27: no free leases
Oct 27 23:43:41 DHCPSRV dhcpd: DHCPDISCOVER from 00:22:15:0d:e7:96 via 
eth0: network 172.16.200.32/27: no free leases
Oct 27 23:43:57 DHCPSRV dhcpd: DHCPDISCOVER from 00:22:15:0d:e7:96 via 
eth0: network 172.16.200.32/27: no free leases
Oct 27 23:48:59 DHCPSRV dhcpd: DHCPDISCOVER from 00:22:15:0d:e7:96 via 
eth0: network 172.16.200.32/27: no free leases

There is a network definition for the server network (172.16.200.32/27) 
which is necessary for the server to run but there is no pool 
statement.  There is nothing on that network except for the server so 
there should be no DHCP requests coming in on eth0.

Why would we be seeing these DISCOVERS coming in from eth0 instead of 
from the router's address?