• State Not Answered
  • Locked Locked
  • Replies 3 replies
  • Subscribers 21 subscribers
  • Views 1343 views
  • Users 0 members are here
2025 survey

We are running a survey to help us improve the experience for all of our members. If you see the survey appear, please take the time to tell us about your experience if you can.

Options
Related
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

tcp/ip: ARP broadcast trailing zeros, fails

Dave Perry

I'm attempting to set up a TCP socket connection using the MCB2300 eval board. The board sends an ARP request, but it is not answered by the gateway. Using Ethereal, I compared the ARP request with one from my PC. One difference is there are 18 trailing zeros in the packet. Is this expected behavior, and could this cause the gateway to ignore the request?

"bad" packet from MCB2300 gets no reply:

0000 ff ff ff ff ff ff 1e 30 6c a2 45 5e 08 06 00 01 .......0 l.E^....
0010 08 00 06 04 00 01 1e 30 6c a2 45 5e c0 a8 6e 36 .......0 l.E^..n6
0020 00 00 00 00 00 00 c0 a8 6e 01 00 00 00 00 00 00 ........ n.......
0030 00 00 00 00 00 00 00 00 00 00 00 00 ........ ....

"good" packet from PC gets a reply:

0000 ff ff ff ff ff ff 00 0d 56 c8 78 62 08 06 00 01 ........V.xb....
0010 08 00 06 04 00 01 00 0d 56 c8 78 62 c0 a8 6e 49 ........V.xb..nI
0020 00 00 00 00 00 00 c0 a8 6e 01 ........n.

  • 0 in reply to Dave Perry

    Are you using a static IP or a dynamic with DHCP enabled?

    For static IP, you might have a misconfigured IP address for MCB2300.

  • 0 in reply to Franc Urbanc

    I am using DHCP. The DHCP assignments are correct, the HTTP server and TFTP work fine. The card responds to ARP queries. It seems there is a problem only when the board needs to initiate the connection.

    I tried to turn off padding in the ethernet driver, with no success. I tried modifying the MAC default register and also the transmit descriptor, using the override bit. It just stopped transmitting at all. I wonder if this feature works in the LPC2368?

    Using Ethereal (now Wireshark), I have seen other devices on the network have the same issue: some (but not all) ARP requests go unanswered. The host in question is running Windows 2003 server. Now I'm wondering if it's an issue with the network.

    I'll post again when I find out more.

    Thanks
    Dave

  • 0 in reply to Dave Perry

    Well it was the proverbial red herring. I was not seeing the arp responses because I was on the wrong side of an ethernet switch.

    Sorry for decreasing the signal to noise ratio...

    Dave