Why is my DeviceMaster offline but responding to ping tests?

Fleetwatch FMS · Network Troubleshooting

DeviceMaster Offline: Ping Test for IP Conflicts

Use this test when the DeviceMaster shows offline in System Monitor and its Comtrol web page isn’t responding. A continuous ping, combined with unplugging the DeviceMaster, tells you whether another device has taken over its IP address or whether the DeviceMaster itself is the problem.

💻 At the computer

You, running the ping on a computer on the same network as the DeviceMaster (such as the Fleetwatch server).

🔧 At the DeviceMaster

A technician who can unplug and reconnect the DeviceMaster’s power while you watch the ping.

Step 1: Start a Continuous Ping

Open Command Prompt: press the Windows key, type cmd, and press Enter. Then type the command below, using the DeviceMaster’s IP address:

C:\> ping -t 192.168.1.50

192.168.1.50 is an example. Replace it with your DeviceMaster’s actual IP address. The -t keeps the ping running until you press Ctrl + C. Leave it running for the rest of the test.

Step 2: Unplug the DeviceMaster and Watch the Ping

Ask the technician to physically disconnect the DeviceMaster from its power source. While it’s powered off, watch the ping results. You’ll see one of two things:

Result A: Replies continue while the DeviceMaster is unplugged

Pinging 192.168.1.50 with 32 bytes of data:
Reply from 192.168.1.50: bytes=32 time=1ms TTL=128
Reply from 192.168.1.50: bytes=32 time<1ms TTL=128
--- DeviceMaster unplugged here ---
Reply from 192.168.1.50: bytes=32 time=1ms TTL=128
Reply from 192.168.1.50: bytes=32 time=1ms TTL=128
Reply from 192.168.1.50: bytes=32 time<1ms TTL=128

What it means: another device is using the DeviceMaster’s IP address.

Something is still answering at that address even though the DeviceMaster is off, so another device has likely taken over the static IP designated for the DeviceMaster.

What to do:

• Contact your network administrator to sort out the conflict and assign the static IP to the DeviceMaster.

• The network admin may ask for the DeviceMaster’s MAC address. The technician can find it on the bottom of the DeviceMaster, or on its web page once it’s back online.

This also explains why the DeviceMaster looked offline: traffic meant for it was going to the other device, even though ping got replies.

Result B: Replies stop when the DeviceMaster is unplugged

Pinging 192.168.1.50 with 32 bytes of data:
Request timed out.
--- DeviceMaster unplugged here ---
Request timed out.
Reply from 192.168.1.10: Destination host unreachable.
Request timed out.

What it means: no other device is using the IP address.

Nothing answers when the DeviceMaster is off, so there’s no IP conflict. Continue to Step 3.

Step 3: Reconnect Power and Check Again

If the replies stopped (Result B), have the technician reconnect the DeviceMaster to power. Give it a minute or two to start up, then watch the ping:

Request timed out.
Request timed out.
--- DeviceMaster plugged back in ---
Request timed out.
Reply from 192.168.1.50: bytes=32 time=2ms TTL=64
Reply from 192.168.1.50: bytes=32 time<1ms TTL=64
Reply from 192.168.1.50: bytes=32 time<1ms TTL=64

When replies return, verify that both of these are working:

☐ The DeviceMaster’s Comtrol web page opens in a browser

☐ The DeviceMaster shows online in System Monitor

✔ Everything works

The power cycle most likely resolved the issue.

✘ Still offline

The DeviceMaster may need to be replaced. Contact Fleetwatch Support.

Tip: See Which Device Is Answering

If you got Result A, you can see the MAC address of the device that’s answering. While the DeviceMaster is still unplugged and the ping is still getting replies, open a second Command Prompt window and run:

C:\> arp -a 192.168.1.50

Interface: 192.168.1.10 --- 0x4
  Internet Address      Physical Address      Type
  192.168.1.50          3c-52-82-1a-2b-3c     dynamic

Compare the Physical Address to the MAC address printed on the bottom of the DeviceMaster. If they don’t match, it confirms another device has the IP. Give this MAC address to your network administrator to help them find that device. Comtrol DeviceMaster MAC addresses typically begin with 00-C0-4E.

This only works when your computer is on the same local network (subnet) as the DeviceMaster.

Quick Reference

Ping result	Next step
Replies continue with the DeviceMaster unplugged	IP conflict. Contact your network administrator, with the DeviceMaster’s MAC address.
Replies stop when unplugged, return when plugged back in, and everything works	Resolved by the power cycle.
Replies stop when unplugged, and it’s still offline after power returns	The DeviceMaster may need to be replaced. Contact Fleetwatch Support.

Questions about DeviceMaster communication? Contact Fleetwatch Support.