dmesg from first kldload: igb0: port 0x6000-0x601f mem 0xd6620000-0xd663ffff,0xd6800000-0xd6bfffff,0xd6600000-0xd6603fff irq 16 at device 0.0 on pci5 igb0: Using MSIX interrupts with 3 vectors igb0: Ethernet address: 90:e2:ba:18:f8:85 igb0: Bound queue 0 to cpu 0 igb0: Bound queue 1 to cpu 1 igb1: port 0x7000-0x701f mem 0xd6c20000-0xd6c3ffff,0xd7000000-0xd73fffff,0xd6c00000-0xd6c03fff irq 17 at device 0.0 on pci6 igb1: Using MSIX interrupts with 3 vectors igb1: Ethernet address: 90:e2:ba:28:0a:47 igb1: Bound queue 0 to cpu 2 igb1: Bound queue 1 to cpu 3 igb0: link state changed to UP tcpdump -n -i igb0 -> absolute silence.......... After some attemtions to connect to this host, sysctl dev.igb.0: dev.igb.0.%desc: Intel(R) PRO/1000 Network Connection version - 2.3.4 dev.igb.0.%driver: igb dev.igb.0.%location: slot=0 function=0 handle=\_SB_.PCI0.PE60.S1F0 dev.igb.0.%pnpinfo: vendor=0x8086 device=0x10c9 subvendor=0x8086 subdevice=0xa03c class=0x020000 dev.igb.0.%parent: pci5 dev.igb.0.nvm: -1 dev.igb.0.enable_aim: 1 dev.igb.0.fc: 3 dev.igb.0.rx_processing_limit: 100 dev.igb.0.link_irq: 0 dev.igb.0.dropped: 0 dev.igb.0.tx_dma_fail: 0 dev.igb.0.rx_overruns: 0 dev.igb.0.watchdog_timeouts: 0 dev.igb.0.device_control: 1488978497 dev.igb.0.rx_control: 67272738 dev.igb.0.interrupt_mask: 4 dev.igb.0.extended_int_mask: 2147483648 dev.igb.0.tx_buf_alloc: 0 dev.igb.0.rx_buf_alloc: 0 dev.igb.0.fc_high_water: 47488 dev.igb.0.fc_low_water: 47472 dev.igb.0.queue0.no_desc_avail: 0 dev.igb.0.queue0.tx_packets: 1 dev.igb.0.queue0.rx_packets: 0 dev.igb.0.queue0.rx_bytes: 0 dev.igb.0.queue0.lro_queued: 0 dev.igb.0.queue0.lro_flushed: 0 dev.igb.0.queue1.no_desc_avail: 0 dev.igb.0.queue1.tx_packets: 0 dev.igb.0.queue1.rx_packets: 0 dev.igb.0.queue1.rx_bytes: 0 dev.igb.0.queue1.lro_queued: 0 dev.igb.0.queue1.lro_flushed: 0 dev.igb.0.mac_stats.excess_coll: 0 dev.igb.0.mac_stats.single_coll: 0 dev.igb.0.mac_stats.multiple_coll: 0 dev.igb.0.mac_stats.late_coll: 0 dev.igb.0.mac_stats.collision_count: 0 dev.igb.0.mac_stats.symbol_errors: 0 dev.igb.0.mac_stats.sequence_errors: 0 dev.igb.0.mac_stats.defer_count: 0 dev.igb.0.mac_stats.missed_packets: 0 dev.igb.0.mac_stats.recv_no_buff: 0 dev.igb.0.mac_stats.recv_undersize: 0 dev.igb.0.mac_stats.recv_fragmented: 0 dev.igb.0.mac_stats.recv_oversize: 0 dev.igb.0.mac_stats.recv_jabber: 0 dev.igb.0.mac_stats.recv_errs: 0 dev.igb.0.mac_stats.crc_errs: 0 dev.igb.0.mac_stats.alignment_errs: 0 dev.igb.0.mac_stats.coll_ext_errs: 0 dev.igb.0.mac_stats.xon_recvd: 0 dev.igb.0.mac_stats.xon_txd: 0 dev.igb.0.mac_stats.xoff_recvd: 0 dev.igb.0.mac_stats.xoff_txd: 0 dev.igb.0.mac_stats.total_pkts_recvd: 122 dev.igb.0.mac_stats.good_pkts_recvd: 20 dev.igb.0.mac_stats.bcast_pkts_recvd: 6 dev.igb.0.mac_stats.mcast_pkts_recvd: 9 dev.igb.0.mac_stats.rx_frames_64: 8 dev.igb.0.mac_stats.rx_frames_65_127: 10 dev.igb.0.mac_stats.rx_frames_128_255: 1 dev.igb.0.mac_stats.rx_frames_256_511: 1 dev.igb.0.mac_stats.rx_frames_512_1023: 0 dev.igb.0.mac_stats.rx_frames_1024_1522: 0 dev.igb.0.mac_stats.good_octets_recvd: 1878 dev.igb.0.mac_stats.good_octets_txd: 64 dev.igb.0.mac_stats.total_pkts_txd: 1 dev.igb.0.mac_stats.good_pkts_txd: 1 dev.igb.0.mac_stats.bcast_pkts_txd: 1 dev.igb.0.mac_stats.mcast_pkts_txd: 0 dev.igb.0.mac_stats.tx_frames_64: 1 dev.igb.0.mac_stats.tx_frames_65_127: 0 dev.igb.0.mac_stats.tx_frames_128_255: 0 dev.igb.0.mac_stats.tx_frames_256_511: 0 dev.igb.0.mac_stats.tx_frames_512_1023: 0 dev.igb.0.mac_stats.tx_frames_1024_1522: 0 dev.igb.0.mac_stats.tso_txd: 0 dev.igb.0.mac_stats.tso_ctx_fail: 0 dev.igb.0.interrupts.asserts: 239 dev.igb.0.interrupts.rx_pkt_timer: 20 dev.igb.0.interrupts.rx_abs_timer: 0 dev.igb.0.interrupts.tx_pkt_timer: 0 dev.igb.0.interrupts.tx_abs_timer: 20 dev.igb.0.interrupts.tx_queue_empty: 1 dev.igb.0.interrupts.tx_queue_min_thresh: 0 dev.igb.0.interrupts.rx_desc_min_thresh: 0 dev.igb.0.interrupts.rx_overrun: 0 dev.igb.0.host.breaker_tx_pkt: 0 dev.igb.0.host.host_tx_pkt_discard: 0 dev.igb.0.host.rx_pkt: 0 dev.igb.0.host.breaker_rx_pkts: 0 dev.igb.0.host.breaker_rx_pkt_drop: 0 dev.igb.0.host.tx_good_pkt: 0 dev.igb.0.host.breaker_tx_pkt_drop: 0 dev.igb.0.host.rx_good_bytes: 1878 dev.igb.0.host.tx_good_bytes: 64 dev.igb.0.host.length_errors: 0 dev.igb.0.host.serdes_violation_pkt: 0 dev.igb.0.host.header_redir_missed: 0 --- dmesg from unloading if_igb and loading again: --- igb0: promiscuous mode disabled igb0: detached pci5: at device 0.0 (no driver attached) igb1: detached pci6: at device 0.0 (no driver attached) igb0: port 0x6000-0x601f mem 0xd6620000-0xd663ffff,0xd6800000-0xd6bfffff,0xd6600000-0xd6603fff irq 16 at device 0.0 on pci5 igb0: Using MSIX interrupts with 3 vectors igb0: Ethernet address: 90:e2:ba:18:f8:85 igb0: Bound queue 0 to cpu 0 igb0: Bound queue 1 to cpu 1 igb1: port 0x7000-0x701f mem 0xd6c20000-0xd6c3ffff,0xd7000000-0xd73fffff,0xd6c00000-0xd6c03fff irq 17 at device 0.0 on pci6 igb1: Using MSIX interrupts with 3 vectors igb1: Ethernet address: 90:e2:ba:28:0a:47 igb1: Bound queue 0 to cpu 2 igb1: Bound queue 1 to cpu 3 igb0: link state changed to UP --- Voila, tcpdump -n -i igb0 after second kldload: 19:26:24.901333 STP 802.1w, Rapid STP, Flags [Forward], bridge-id 8000.d0:7e:28:09:f0:a9.8004, length 47 19:26:26.083915 IP 172.21.1.9.1049 > 229.111.112.12.3071: UDP, length 4 19:26:26.980663 STP 802.1w, Rapid STP, Flags [Forward], bridge-id 8000.d0:7e:28:09:f0:a9.8004, length 47 19:26:27.925346 d0:7e:28:09:f0:ae > 01:80:c2:00:00:0a, ethertype Unknown (0x88a7), length 167: 0x0000: 0003 0000 01b4 be4c 0001 000e 0000 0000 .......L........ 0x0010: d07e 2809 f0a9 0007 0017 4850 2056 3139 .~(.......HP.V19 0x0020: 3130 2d31 3647 2053 7769 7463 6800 0e00 10-16G.Switch... 0x0030: 1352 656c 6561 7365 2031 3531 3250 3130 .Release.1512P10 0x0040: 0011 0013 5631 3030 5230 3035 4230 3944 ....V100R005B09D 0x0050: 3031 3300 1000 0731 3538 000c 0014 1000 013....158...... 0x0060: 0000 0000 0000 0000 0000 0000 0000 0003 ................ 0x0070: 000d 6870 7377 6974 6368 3100 0200 1847 ..hpswitch1....G 0x0080: 6967 6162 6974 4574 6865 726e 6574 312f igabitEthernet1/ 0x0090: 302f 3400 0b00 0600 03 0/4...... 19:26:28.457955 IP 172.21.1.30.1048 > 229.111.112.12.3071: UDP, length 4 19:26:28.939911 STP 802.1w, Rapid STP, Flags [Forward], bridge-id 8000.d0:7e:28:09:f0:a9.8004, length 47 19:26:30.900036 STP 802.1w, Rapid STP, Flags [Forward], bridge-id 8000.d0:7e:28:09:f0:a9.8004, length 47 19:26:31.100442 IP 172.21.1.9.1049 > 229.111.112.12.3071: UDP, length 4 19:26:32.900543 STP 802.1w, Rapid STP, Flags [Forward], bridge-id 8000.d0:7e:28:09:f0:a9.8004, length 47 19:26:33.457873 IP 172.21.1.30.1048 > 229.111.112.12.3071: UDP, length 4 19:26:34.899814 STP 802.1w, Rapid STP, Flags [Forward], bridge-id 8000.d0:7e:28:09:f0:a9.8004, length 47 19:26:35.016611 IP 172.21.3.1 > 172.21.3.97: ICMP echo request, id 39989, seq 0, length 64 19:26:36.019143 IP 172.21.3.1 > 172.21.3.97: ICMP echo request, id 39989, seq 1, length 64 19:26:36.114576 IP 172.21.1.9.1049 > 229.111.112.12.3071: UDP, length 4 19:26:36.900648 STP 802.1w, Rapid STP, Flags [Forward], bridge-id 8000.d0:7e:28:09:f0:a9.8004, length 47