title: Can't ping internally connected vm
body: <p>I have three vms running with virtual box. <br>
   <br>
  The first one (VM1) has two network adapters set to:Internal network. Lets say the first adapter (eth19) is connected to internal network with name "int1" and the second adapter (eth20) is  connected to internal network with name "int2".
   <br>
   <br>
  The second vm (VM2) has one network adapter( eth21 ) that is connected to internal network with name "int1" and finnally the third vm (VM3)  has one network adapter( eth25 ) that is connected to internal network with name "int2".</p>
  
  <p>i set the ip addresses manually as following</p>
  
  <pre><code>(VM1): ifconfig eth19 10.0.0.1
         ifconfig eth20 10.0.0.10
  output:
  eth19 Link encap:Ethernet  HWaddr 08:00:27:e1:ad:2b  
        inet addr:10.0.0.1  Bcast:10.0.0.255  Mask:255.255.255.0
        inet6 addr: fe80::a00:27ff:fee1:ad2b/64 Scope:Link
        UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
        RX packets:14 errors:0 dropped:0 overruns:0 frame:0
        TX packets:94 errors:0 dropped:0 overruns:0 carrier:0
        collisions:0 txqueuelen:1000 
        RX bytes:1259 (1.2 KiB)  TX bytes:10022 (9.7 KiB)
  
  eth20 Link encap:Ethernet  HWaddr 08:00:27:e9:66:66  
        inet addr:10.0.0.10  Bcast:10.0.0.255  Mask:255.255.255.0
        inet6 addr: fe80::a00:27ff:fee9:6666/64 Scope:Link
        UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
        RX packets:25 errors:0 dropped:0 overruns:0 frame:0
        TX packets:36 errors:0 dropped:0 overruns:0 carrier:0
        collisions:0 txqueuelen:1000 
        RX bytes:5741 (5.6 KiB)  TX bytes:6775 (6.6 KiB)
  
   Kernel IP routing table
   Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
   10.0.0.0        0.0.0.0         255.255.255.0   U     0      0        0 eth19
   10.0.0.0        0.0.0.0         255.255.255.0   U     0      0        0 eth20
  
  
  (VM2): ifconfig eth21 10.0.0.2
  
  eth21 Link encap:Ethernet  HWaddr 08:00:27:65:7b:83  
        inet addr:10.0.0.2  Bcast:10.0.0.255  Mask:255.255.255.0
        inet6 addr: fe80::a00:27ff:fe65:7b83/64 Scope:Link
        UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
        RX packets:85 errors:0 dropped:0 overruns:0 frame:0
        TX packets:49 errors:0 dropped:0 overruns:0 carrier:0
        collisions:0 txqueuelen:1000 
        RX bytes:10002 (9.7 KiB)  TX bytes:7816 (7.6 KiB)
  
  Kernel IP routing table
  Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
  10.0.0.0        0.0.0.0         255.255.255.0   U     0      0        0 eth21
  
  
  
  (VM3): ifconfig eth25 10.0.0.3
  
  eth25 Link encap:Ethernet  HWaddr 08:00:27:ae:77:cd  
        inet addr:10.0.0.3  Bcast:10.0.0.255  Mask:255.255.255.0
        inet6 addr: fe80::a00:27ff:feae:77cd/64 Scope:Link
        UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
        RX packets:0 errors:0 dropped:0 overruns:0 frame:0
        TX packets:32 errors:0 dropped:0 overruns:0 carrier:0
        collisions:0 txqueuelen:1000 
        RX bytes:0 (0.0 B)  TX bytes:6303 (6.1 KiB)
  
  Kernel IP routing table
  Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
  10.0.0.0        0.0.0.0         255.255.255.0   U     0      0        0 eth25
  </code></pre>
  
  <p>i can ping from VM1 to VM2 and from VM2 to VM1 but i cant ping VM3.</p>
  
  <p>ping from VM1 to VM3:</p>
  
  <pre><code>ping 10.0.0.3
  PING 10.0.0.3 (10.0.0.3) 56(84) bytes of data.
  From 10.0.0.1 icmp_seq=1 Destination Host Unreachable
  From 10.0.0.1 icmp_seq=2 Destination Host Unreachable
  From 10.0.0.1 icmp_seq=3 Destination Host Unreachable
  </code></pre>
  
  <p>what can be wrong?</p>
  
  <p>EDIT<br>
      arping VM1 to VM3 </p>
  
  <pre><code>arping -I eth20 -c 2 10.0.0.3
  ARPING 10.0.0.3
  60 bytes from 08:00:27:ae:77:cd (10.0.0.3): index=0 time=667.000 usec
  60 bytes from 08:00:27:ae:77:cd (10.0.0.3): index=1 time=448.000 usec
  
  --- 10.0.0.3 statistics ---
  2 packets transmitted, 2 packets received,   0% unanswered (0 extra)
  </code></pre>
  
  <p>arping VM1 to VM2</p>
  
  <pre><code>arping -I eth19 -c 2 10.0.0.2
  ARPING 10.0.0.2
  60 bytes from 08:00:27:65:7b:83 (10.0.0.2): index=0 time=330.000 usec
  60 bytes from 08:00:27:65:7b:83 (10.0.0.2): index=1 time=622.000 usec
  
  --- 10.0.0.2 statistics ---
  2 packets transmitted, 2 packets received,   0% unanswered (0 extra)
  </code></pre>