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IGMP seen but can’t ping

0

Hello I see on Wireshark an embedded board on which I want to connect. I successful connect to the board if its cable is connected after its startup. However if the cable is connected during the startup process, I can not ping it. This seems to happen only on some configurations (with a moxa hub on which POE devices are connected). Using wireshark I can see that the board is sending 2 IGMP messages in both configuration ( cable connected at startup and cable connected after startup).

IGMP message show the correct ip address in both case

asked 21 Oct '14, 12:32

J%C3%A9r%C3%A9mie%20Guillot's gravatar image

Jérémie Guillot
11●1●1●3
accept rate: 0%

One Answer:

1

However if the cable is connected during the startup process, I can not ping it.

If you cannot ping the board, there could be several reasons, like:

  • The embedded board is not answering ARP requests
  • Your client (somehow) has the wrong MAC address in its ARP cache
  • There is a problem with the initialization of either the NIC or the IP stack within the embedded board

So, to rule out some possible problems, please do the following:

  • start Wireshark
  • ping the system
  • stop Wireshark
  • check the captured data for: ARP request/response, ICMP ECHO request/response (ping), the correct MAC address in those frames.

If you see the ICMP ECHO request being sent to the correct MAC address, but you don't see any answer, it's a problem with the board (either NIC or IP stack). Then Wireshark can't help you any further.

If you don't see an ICMP ECHO request, you client does not know where to send it, so it does not get an answer for it's ARP request (check that in the capture file as well). Again: probably a problem within the embedded board.

Regards
Kurt

answered 22 Oct '14, 05:35

Kurt%20Knochner's gravatar image

Kurt Knochner ♦
24.8k●10●39●237
accept rate: 15%

Hello kurt and thanks for your help.

You're right there's no answer to the arp request. So it seems there's a problem with the embedded board. The strange thing is that IGMPv2 message is received...

(24 Oct '14, 03:46) Jérémie Guillot

If it's a bug, the behaviour will likely be 'strange', so the fact that the systems sends out frames does not mean it is also able to receive frames ;-))

(26 Oct '14, 15:36) Kurt Knochner ♦