Issues with transferring files from switch to TFTPd64

[Skjoedt]

Hello

I don't know if this is the right forum, but i recently switched to Windows 11 and ever since i have been having issues with transferring a file from a switch to my computer via TFTP, for example a config backup using the command "copy start tftp".

There is IP-connectivity and the first initial connection is established, however, no data is transferred.

I am a Local Admin, the program is run as admin and i have disabled all windows firewall profiles.

Switch-3650#copy startup-config tftp:
Address or name of remote host []? 172.16.0.213
Destination filename [switch-3650-confg]?
!.....
%Error writing tftp://172.16.0.213/switch-3650-confg (Timed out).....
Switch-3650#

Is Windows 11 doing something weird when a connection is redirected to a high-port?

I hope somebody is able to help!

Best Regards
Frederik

[Richard Burts]

Frederik

This forum is one of several where your question would be appropriate.

Am I correct in understanding that this computer was running Windows 10 and tftpd64 was working fine. Then you upgraded to Windows 11 and it stopped working?

That suggests that there is something release level specific. I wonder if downloading and installing a new copy of tftpd64 would be helpful?

If the problem continues I wonder if running debug for tftp on the switch might provide any helpful information?

[Skjoedt]

Hello Rick

Thank you getting back to me.

Almost, i have switched computers...
On my old Windows 10 Laptop i was using TFTPd64 for working with files on switches.
Now i have a new laptop for work, which runs Windows 11 and now i am having issues.

However, it is only when writing files to disk on the laptop, not when I am downloading files from the laptop to the switch.

I did just that, went to github and downloaded and installed ver. 4.64 of tftpd64.

I tried to do a packet capture on wireshark, and my laptop is receiving packets on port 50000, but no reply and my laptop is sending ICMP destination unreachable (Port unavailable) back to the switch.
- But only when windows firewall is off, if is switch on windows firewall, then the ICMP packets are suppressed.

I can't attach a packet capture, so i have attached a screenshot instead.

[Richard Burts]

Thanks for the additional information. The screen shot is interesting. Clearly the switch is sending to the PC. There is a request from the switch to the PC. There is a positive response from the PC to the switch. The switch sends a data packet and the PC responds port unavailable. So there is pretty obviously something on the PC. My guess is that it is something about write permission to that directory of the PC.

[Skjoedt]

Hello Rick

That is also my opinion, that it is something with the PC...
- And that is how i arrive at this post... I simply can't figure out what i need to change on my PC, in order to get this working...
I was hoping somebody on this forum had experienced the same thing and solved it...

Best Regards
Frederik

[Georg Pauwen · Accepted solution]

Hello,

in addition to @Richard Burts remarks, you could try a different (default is 512 I think) tftp block size:

ip tftp blocksize 

Also, check if the Windows firewall is not blocking the TFTP server:

https://www.intel.com/content/www/us/en/docs/programmable/683536/current/enabling-the-tftp-server-through-the.html

[Skjoedt]

Hello Georg

Awesome! I will try it out with a different block size and let you know

The Windows Firewall is disabled when testing, see the packet capture i have attached in another reply

Best Regards
Frederik

[Skjoedt]

Hello Georg

Changing the blocksize seemed to do the trick, i can transfer the file now!

Thank you for your help!

Switch-3650#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch-3650(config)#
Switch-3650(config)#ip tftp blocksize ?
<512-8192> blocksize value

Switch-3650(config)#ip tftp blocksize 512
Switch-3650(config)#end
Switch-3650#
Switch-3650#copy startup-config tftp:
Address or name of remote host []? 172.16.0.213
Destination filename [switch-3650-confg]?
!!
15629 bytes copied in 0.124 secs (126040 bytes/sec)
Switch-3650#

[Georg Pauwen]

Hello,

odd...as 512 is supposed to be the default. Either way, glad that it is working now !

[balaji.bandi · Accepted solution]

check the my blog for the block size :

https://www.balajibandi.com/?p=1713

EDIT - lately read@Georg Pauwen reply - he was suggesting same.

[Skjoedt]

Hello Balaji

Thank you for the link to your blog, i will try it out and get back to you!

Best Regards
Frederik

[Skjoedt]

Changing the blocksize seemed to do the trick, i can transfer the file now!

Thank you for your help!

Switch-3650#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch-3650(config)#
Switch-3650(config)#ip tftp blocksize ?
<512-8192> blocksize value

Switch-3650(config)#ip tftp blocksize 512
Switch-3650(config)#end
Switch-3650#
Switch-3650#copy startup-config tftp:
Address or name of remote host []? 172.16.0.213
Destination filename [switch-3650-confg]?
!!
15629 bytes copied in 0.124 secs (126040 bytes/sec)
Switch-3650#