Why the responses sent from the tftp server are not received successfully to the tftp client ?

Solution Verified - Updated -

Issue

  • tftp client is not receiving any reply from tftp server.
  • When checked in tcpdump, can see that tftp server is responding properly but those responses are not reaching tftp client.
  • Below is the tcpdump from tftp server where it is seen that server is responding to the requests by sending Option Acknowledgement:
NO. Time        Source      Destination Protocol    Info
1   0.000000    66.180.X.X  168.215.X.X TFTP        Read Request, File: motd\000, Transfer type: octet\000, tsize\000=0\000, rollover\000=0\000
2   0.020466    168.215.X.X 66.180.X.X  TFTP        Option Acknowledgement, tsize\000=40\000
3   1.021749    168.215.X.X 66.180.X.X  TFTP        Option Acknowledgement, tsize\000=40\000
4   3.023881    168.215.X.X 66.180.X.X  TFTP        Option Acknowledgement, tsize\000=40\000
5   4.999208    66.180.X.X  168.215.X.X TFTP        Read Request, File: motd\000, Transfer type: octet\000, tsize\000=0\000, rollover\000=0\000
6   5.001073    168.215.X.X 66.180.X.X  TFTP        Option Acknowledgement, tsize\000=40\000
7   6.002286    168.215.X.X 66.180.X.X  TFTP        Option Acknowledgement, tsize\000=40\000
8   7.028005    168.215.X.X 66.180.X.X  TFTP        Option Acknowledgement, tsize\000=40\000
9   8.004478    168.215.X.X 66.180.X.X  TFTP        Option Acknowledgement, tsize\000=40\000
10  9.999266    66.180.X.X  168.215.X.X TFTP        Read Request, File: motd\000, Transfer type: octet\000, tsize\000=0\000, rollover\000=0\000
11  10.001341   168.215.X.X 66.180.X.X  TFTP        Option Acknowledgement, tsize\000=40\000
  • Below is the tcpdump captured from tftp client where only generated requests are seen but no responses OR Option Acknowledgement sent by server are not seen:
NO. Time        Source      Destination Protocol    Info
1   0.000000    66.180.X.X  168.215.X.X TFTP        Read Request, File: motd\000, Transfer type: octet\000, tsize\000=0\000, rollover\000=0\000
2   4.999331    66.180.X.X  168.215.X.X TFTP        Read Request, File: motd\000, Transfer type: octet\000, tsize\000=0\000, rollover\000=0\000
3   9.999477    66.180.X.X  168.215.X.X TFTP        Read Request, File: motd\000, Transfer type: octet\000, tsize\000=0\000, rollover\000=0\000

Environment

  • Red Hat Enterprise Linux 6.2
  • kernel-2.6.32-220.el6.x86_64
  • vmxnet3 driver version: 1.1.18.0-k-NAPI
  • tftp client server communication.

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