In a Linux DHCP server I'm getting a bunch of these log lines:

dhcpd: DHCPDISCOVER from 00:30:48:fe:5c:9c via eth1: network 192.168.2.0/24: no free leases

I don't have any machines with 00:30:48:fe:5c:9c and I don't intend to give out an IP to 00:30:48:fe:5c:9c (whatever that could be).

I tracked down the server that this is coming from and killed all the DHCP clients that were running but the DHCPDISCOVER requests do not stop.

I can prove that this is the sending server by pulling the Ethernet cable - the requests stop.

The strange thing is that the sending server only has 2 interfaces which are:

• 00:30:48:fe:5c:9a
• 00:30:48:fe:5c:9b

What can be the cause of the off-by-one address? Who could be sending the requests?

Details

On the DHCP client:

root@n34:~# ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 100
    link/ether 00:30:48:fe:5c:9a brd ff:ff:ff:ff:ff:ff
3: eth1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN qlen 1000
    link/ether 00:30:48:fe:5c:9b brd ff:ff:ff:ff:ff:ff
4: ib0: <BROADCAST,MULTICAST> mtu 2044 qdisc noop state DOWN qlen 256
    link/infiniband 80:00:00:48:fe:80:00:00:00:00:00:00:00:02:c9:03:00:08:81:9f brd 00:ff:ff:ff:ff:12:40:1b:ff:ff:00:00:00:00:00:00:ff:ff:ff:ff
5: ib1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 2044 qdisc pfifo_fast state UP qlen 256
    link/infiniband 80:00:00:49:fe:80:00:00:00:00:00:00:00:02:c9:03:00:08:81:a0 brd 00:ff:ff:ff:ff:12:40:1b:ff:ff:00:00:00:00:00:00:ff:ff:ff:ff

Same info:

root@n34:~# ifconfig -a
eth0      Link encap:Ethernet  HWaddr 00:30:48:fe:5c:9a  
          inet addr:192.168.2.234  Bcast:192.168.2.255  Mask:255.255.255.0
          inet6 addr: fe80::230:48ff:fefe:5c9a/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:72544 errors:0 dropped:0 overruns:0 frame:0
          TX packets:152773 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100 
          RX bytes:4908592 (4.6 MiB)  TX bytes:89815782 (85.6 MiB)
          Memory:dfd60000-dfd80000 

eth1      Link encap:Ethernet  HWaddr 00:30:48:fe:5c:9b  
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          Memory:dfde0000-dfe00000 

ib0       Link encap:UNSPEC  HWaddr 80-00-00-48-FE-80-00-00-00-00-00-00-00-00-00-00  
          BROADCAST MULTICAST  MTU:2044  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:256 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

ib1       Link encap:UNSPEC  HWaddr 80-00-00-49-FE-80-00-00-00-00-00-00-00-00-00-00  
          inet addr:192.168.3.234  Bcast:192.168.3.255  Mask:255.255.255.0
          inet6 addr: fe80::202:c903:8:81a0/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:2044  Metric:1
          RX packets:1330 errors:0 dropped:0 overruns:0 frame:0
          TX packets:255 errors:0 dropped:5 overruns:0 carrier:0
          collisions:0 txqueuelen:256 
          RX bytes:716415 (699.6 KiB)  TX bytes:17584 (17.1 KiB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:8 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:560 (560.0 B)  TX bytes:560 (560.0 B)

The nodes were imaged with Perseus which uses kexec instead of rebooting.