Using the ARPING Tool to Test Network Connectivity

As of IBM i 7.1 and via PTFs (SI31691 and its requisites) in IBM i 6.1, a tool called ARPING (Send ARP Request, SNDARPRQS) is now supported. Like its LINUX counterpart, this tool can be used to test connectivity to an IP address on a local TCP/IP network. The tool is similar to the PING (Verify TCP/IP Connection) tool, except that it uses the Address Resolution Protocol (ARP) rather than the Internet Control Message Protocol (ICMP). Unlike ICMP messages, ARP messages aren’t routable, so this command will only work for IP addresses in the local network.

The tool requires two parameters. The remote IP address to probe, and the local Ethernet line to use.  At least one local TCP/IP interface must be active on the line used. If the remote IP address exists and responds to an ARP REQUEST message, the tool will produce output such as the following:

  4 > ARPING INTNETADR('10.5.176.160') LIND(ETHLINE)        
      Sending ARP request to 10.5.176.160 using line ETHLINE.
      Reply from [3C:DF:1E:8C:0C:00] took 2 ms.            
      Reply from [3C:DF:1E:8C:0C:00] took 1 ms.            
      Reply from [3C:DF:1E:8C:0C:00] took 1 ms.            
      ARP request statistics: 3 of 3 successful (100 %).   

A successful reply message will include the MAC address of the host that responded to the ARP message and the time in milliseconds that it took to receive the response. If there’s no connectivity to the IP address on the local network or the host is unable to respond, ARPING will produce output such as the following:

  4 > ARPING INTNETADR('10.5.176.160') LIND(VETH0)        
      Sending ARP request to 10.5.176.160 using line VETH0.
      No response from 10.5.176.160 within 1 seconds.     
      No response from 10.5.176.160 within 1 seconds.     
      No response from 10.5.176.160 within 1 seconds.     
      ARP request statistics: 0 of 3 successful (0 %).   


I'd like to thank Clair Wood who works on the IBM i Networking team for writing this week's blog.

Twitter: #ibmi @DawnMayiCan #COMMONUG, #ibmiuser