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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 em1"

When 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 Table

thegorlie@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 p3p1

ifconfig

em1       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-f7e20000

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: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:19

ARP manual request

thegorlie@serv-io ~> arping -c 1 -I em1 192.168.100.20
ARPING 192.168.100.20 from 192.168.100.1 em1
Sent 1 probes (1 broadcast(s))
Received 0 response(s)

Wireshark capture on the host when server ping the host

Giga-Byt_e7:62:16   Broadcast   ARP 60  Who has 192.168.100.20?  Tell 192.168.100.1
Sony_c8:7a:a3   Giga-Byt_e7:62:16   ARP 42  192.168.100.20 is at 30:f9:ed:c8:7a:a3
Giga-Byt_e7:62:16   Broadcast   ARP 60  Who has 192.168.100.20?  Tell 192.168.100.1
Sony_c8:7a:a3   Giga-Byt_e7:62:16   ARP 42  192.168.100.20 is at 30:f9:ed:c8:7a:a3
Giga-Byt_e7:62:16   Broadcast   ARP 60  Who has 192.168.100.20?  Tell 192.168.100.1
Sony_c8:7a:a3   Giga-Byt_e7:62:16   ARP 42  192.168.100.20 is at 30:f9:ed:c8:7a:a3

Wireshark capture on the host when host ping the server

Sony_c8:7a:a3   Broadcast   ARP 42  Who has 192.168.100.1?  Tell 192.168.100.20
Sony_c8:7a:a3   Broadcast   ARP 42  Who has 192.168.100.1?  Tell 192.168.100.20
Sony_c8:7a:a3   Broadcast   ARP 42  Who has 192.168.100.1?  Tell 192.168.100.20
Sony_c8:7a:a3   Broadcast   ARP 42  Who has 192.168.100.1?  Tell 192.168.100.20
Sony_c8:7a:a3   Broadcast   ARP 42  Who has 192.168.100.1?  Tell 192.168.100.20
  • Presumably, the xx:xx after the :e7: in the MAC addresses are different for the two interfaces? Is there a security benefit in redacting your MAC address? They are local to your network. If you must, consider hiding the first half and displaying the second as it provides more information. Or redacting a portion in the middle maybe? – garethTheRed Nov 9 '14 at 9:08
  • Yes they are different. You're right, I'm going to change this. Thanks – IGassmann Nov 9 '14 at 9:37
1

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.

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