I setup to log packets from the OS MAC address. I see a continuous stream that looks like the following where:
OS MAC address = 00:1e:c0:d7:2b:bd
192.168.1.32 is the OS IP address (via DHCP reservation)
These are DHCP requests
Jun 1 19:40:16 Rotary kernel: [LAN_Local-30-A]IN=eth1 OUT= MAC=ff:ff:ff:ff:ff:ff:00:1e:c0:d7:2b:bd:08:00 SRC=192.168.1.32 DST=255.255.255.255 LEN=305 TOS=
0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=UDP SPT=68 DPT=67 LEN=285
Jun 1 19:40:17 Rotary kernel: [LAN_Local-30-A]IN=eth1 OUT= MAC=ff:ff:ff:ff:ff:ff:00:1e:c0:d7:2b:bd:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=293 TOS=0x00
PREC=0x00 TTL=64 ID=0 DF PROTO=UDP SPT=68 DPT=67 LEN=273
Jun 1 19:40:17 Rotary kernel: [LAN_Local-30-A]IN=eth1 OUT= MAC=ff:ff:ff:ff:ff:ff:00:1e:c0:d7:2b:bd:08:00 SRC=192.168.1.32 DST=255.255.255.255 LEN=305 TOS=
0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=UDP SPT=68 DPT=67 LEN=285
Jun 1 19:40:18 Rotary kernel: [LAN_Local-30-A]IN=eth1 OUT= MAC=ff:ff:ff:ff:ff:ff:00:1e:c0:d7:2b:bd:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=293 TOS=0x00
PREC=0x00 TTL=64 ID=0 DF PROTO=UDP SPT=68 DPT=67 LEN=273
Jun 1 19:40:18 Rotary kernel: [LAN_Local-30-A]IN=eth1 OUT= MAC=ff:ff:ff:ff:ff:ff:00:1e:c0:d7:2b:bd:08:00 SRC=192.168.1.32 DST=255.255.255.255 LEN=305 TOS=
0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=UDP SPT=68 DPT=67 LEN=285
Jun 1 19:40:19 Rotary kernel: [LAN_Local-30-A]IN=eth1 OUT= MAC=ff:ff:ff:ff:ff:ff:00:1e:c0:d7:2b:bd:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=293 TOS=0x00
PREC=0x00 TTL=64 ID=0 DF PROTO=UDP SPT=68 DPT=67 LEN=273