Who would have thought that a simple PING command could ever cause any problems?
There have been many occasions when I've tested network connections using this simple command and even used a Ping utility like Angry IP Scanner to see what IP addresses were active.
Well, you can only imaging my surprise when all hell broke loose whilst investigating a problem with an Epson TM-U220 Printer fitted with an Ethernet Interface.
We had several printers connected to an isolated network that had been setup for a demonstration. One of the printers (not an Epson) had stopped working and I was asked to investigate. None of the original configuration had changed since the earlier demo where it was left in a working condition.
I used the Ping utility to test for responding equipment and observed the Epson TM-U220 print a configuration ticket that showed the IP address had changed. This only occurred occasionally.
Eventually, I discovered that this only happened when the Ping utility was set to scan all the IP addresses on the subnet including the broadcast IP (EG 192.168.1.255).
At first I thought that there could be a fault with the utility that caused this strange problem with the printer. To test this theory, I performed a PING from the command prompt that fortunately had the same affect and caused the printer to print another configuration ticket.
The first problem was that each time the printer was reconfigured, it was set to use the broadcast address. The implication of this is that, every machine on the same subnet hears any message sent to the broadcast IP. Imagine sending a print request to the broadcast IP and having all the printers print the same message!
The second problem is that, once set to the broadcast address, the normal programming utilities would not work, they couldn’t connect to the broadcast address.
I realised that we had to connect using the hardware (MAC) address but hadn’t done this before. As we were running out of time, I prepared two other replacement printers. This left me with the challenge of fixing the problem printers in my spare time.
With some help from a colleague, we eventually discovered that we could get the printer back to its correct IP address using a combination of ARP (Address Resolution Protocol) and PING commands.
This is how:
Make a note of the printers Ethernet Address, this was printed on the configuration ticket. You can often force the printer to print this information by pressing the reset button near the RJ45 socket of the network card. There may also be a label by the port stating this address.
Once you known the Ethernet address of the printer, simply use the ARP command as follows:
arp -s 192.168.0.173 00-20-7F-CB-37-77
This command tells the printer that has a Ethernet address of 00-20-7F-CB-37-77 to change its IP address to 192.168.0.173.
To actually change the IP address of the printer, use the PING command to send the ARP information just specified as follows:
PING 192.168.0.173
The above procedure would add an entry to the ARP table on the PC from which the command was performed. This can be deleted as follows:
arp -d 192.168.0.173
The printer should now have the required IP address and should connect to the configuration software should any further changes be required.
I am sure that this problem is not specific to the Epson printer however, this is my first experience of what could have been a major problem.
It is also worth noting that the configuration software also has an option to disable programming by PING although I do not know the implications of disabling this.
In my search for a solution, I found the following references useful:
I hope this saves someone the torment we suffered.
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