I have a server with two NIC and it's running Ubuntu Server 14.04. The first one is the interface p3p1 and it's connected to the subnet 192.168.1.0/24 with the IP 192.168.1.100. The second one is the interface em1 and it's connected to the subnet 192.168.100.0/24 with the IP 192.168.100.1.My server can ping all the hosts of the subnet 192.168.1.0/24, but it can't ping the hosts of 192.168.100.0/24.When I try to ping to host (192.168.100.20) on the subnet 192.168.100.0/24, I can see the ARP requests of my server and the ARP response of the host telling his MAC address to the server. But when I try to see the arp table of the server, it's telling: ? (192.168.100.20) at <incomplete> on em1When I try to ping to the server (192.168.100.1) with the host (192.168.1.20), I can see the ARP requests of my host, but I don't get responses of the server.If I add manually the MAC address of the host on the server ARP table, the ping works.I think the ARP service it doesn't work for the em1 interface, but I don't know how to repair.There is my config :ARP Tablethegorlie@serv-io ~> arp -a? (192.168.100.20) at <incomplete> on em1? (192.168.1.1) at e0:ce:c3:f5:be:56 [ether] on p3p1? (192.168.1.14) at 08:3e:8e:dd:05:e7 [ether] on p3p1ifconfigem1       Link encap:Ethernet  HWaddr 74:d4:35:e7:62:16          inet addr:192.168.100.1  Bcast:192.168.100.255  Mask:255.255.255.0          inet6 addr: xxxx::xxxx:35ff:fee7:6216/64 Scope:Link          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1          RX packets:0 errors:0 dropped:0 overruns:0 frame:0          TX packets:72 errors:0 dropped:0 overruns:0 carrier:0          collisions:0 txqueuelen:1000          RX bytes:0 (0.0 B)  TX bytes:5422 (5.4 KB)          Interrupt:20 Memory:f7e00000-f7e20000lo        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:65536  Metric:1          RX packets:909 errors:0 dropped:0 overruns:0 frame:0          TX packets:909 errors:0 dropped:0 overruns:0 carrier:0          collisions:0 txqueuelen:0          RX bytes:91970 (91.9 KB)  TX bytes:91970 (91.9 KB)p3p1      Link encap:Ethernet  HWaddr 74:d4:35:e7:62:14          inet addr:192.168.1.100  Bcast:192.168.1.255  Mask:255.255.255.0          inet6 addr: xxxx:xxxx:xxxx:3a80:76d4:35ff:fee7:6214/64 Scope:Global          inet6 addr: xxxx::xxxx:xxxx:fee7:6214/64 Scope:Link          inet6 addr: xxxx:xxxx:xxxx:3a80:2d32:f878:e435:69ec/64 Scope:Global          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1          RX packets:0 errors:0 dropped:27756 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)          Interrupt:19ARP manual requestthegorlie@serv-io ~> arping -c 1 -I em1 192.168.100.20ARPING 192.168.100.20 from 192.168.100.1 em1Sent 1 probes (1 broadcast(s))Received 0 response(s)Wireshark capture on the host when server ping the hostGiga-Byt_e7:62:16   Broadcast   ARP 60  Who has 192.168.100.20?  Tell 192.168.100.1Sony_c8:7a:a3   Giga-Byt_e7:62:16   ARP 42  192.168.100.20 is at 30:f9:ed:c8:7a:a3Giga-Byt_e7:62:16   Broadcast   ARP 60  Who has 192.168.100.20?  Tell 192.168.100.1Sony_c8:7a:a3   Giga-Byt_e7:62:16   ARP 42  192.168.100.20 is at 30:f9:ed:c8:7a:a3Giga-Byt_e7:62:16   Broadcast   ARP 60  Who has 192.168.100.20?  Tell 192.168.100.1Sony_c8:7a:a3   Giga-Byt_e7:62:16   ARP 42  192.168.100.20 is at 30:f9:ed:c8:7a:a3Wireshark capture on the host when host ping the serverSony_c8:7a:a3   Broadcast   ARP 42  Who has 192.168.100.1?  Tell 192.168.100.20Sony_c8:7a:a3   Broadcast   ARP 42  Who has 192.168.100.1?  Tell 192.168.100.20Sony_c8:7a:a3   Broadcast   ARP 42  Who has 192.168.100.1?  Tell 192.168.100.20Sony_c8:7a:a3   Broadcast   ARP 42  Who has 192.168.100.1?  Tell 192.168.100.20Sony_c8:7a:a3   Broadcast   ARP 42  Who has 192.168.100.1?  Tell 192.168.100.20
Network interface not registring ARP response
linux;ubuntu;networking;networkcard;arp
I found the problem.The problem was the driver that had some bugs. I downloaded the most recent version of the drivers for my ethernet card (Intel Ethernet Connection I217-V) embedded in the motherboard (GA-Z97N-WIFI) and installed it. It works with no problem.