Test machine 1: ( sender ) OS: FreeBSD 10.0 We are using below Emulex skyhawk adapter. oce0@pci0:4:0:0: class=0x020000 card=0xe80110df chip=0x072010df rev=0x10 hdr=0x00 vendor = 'Emulex Corporation' device = 'OneConnect NIC (Skyhawk)' class = network subclass = ethernet bar [10] = type Prefetchable Memory, range 64, base rxfb340000, size 16384, enabled bar [18] = type Prefetchable Memory, range 64, base rxfb320000, size 131072, enabled bar [20] = type Prefetchable Memory, range 64, base rxfb300000, size 131072, enabled Test machine 2: ( receiver ) OS: FreeBSD 10.0 We are using below Emulex skyhawk adapter. oce0@pci0:4:0:0: class=0x020000 card=0xe80110df chip=0x072010df rev=0x10 hdr=0x00 vendor = 'Emulex Corporation' device = 'OneConnect NIC (Skyhawk)' class = network subclass = ethernet bar [10] = type Prefetchable Memory, range 64, base rxfb340000, size 16384, enabled bar [18] = type Prefetchable Memory, range 64, base rxfb320000, size 131072, enabled bar [20] = type Prefetchable Memory, range 64, base rxfb300000, size 131072, enabled Steps to Reproduce: 1. Both the above cards are connected directly without switch. 2. Configure interfaces. 3. Issue ping on Machine 1 ( sender ). It is able to ping receiver. 4. While ping continues, on Machine 1 (sender), change MAC addr Original MAC: 00:90:fa:6c:18:08 Changed MAC using "ifconfig oce0 ether ab:90:fa:6c:18:08" Changed first two bits 00 => ab. 5. Ping stops working. 6. In tcpdump if we see, it still shows old mac address. We are observing this behavior even with other adapters like Intel igb0@pci0:2:0:0: class=0x020000 card=0x152115d9 chip=0x15218086 rev=0x01 hdr=0x00 vendor = 'Intel Corporation' device = 'I350 Gigabit Network Connection' class = network subclass = ethernet bar [10] = type Memory, range 32, base rxfbc20000, size 131072, enabled bar [18] = type I/O Port, range 32, base rxe020, size 32, enabled bar [1c] = type Memory, range 32, base rxfbc44000, size 16384, enabled