Symptom
TFTP to switch with ip tftp block size as 8192 unable to copy the files, By default ip tftp block size 8192 and while we are trying to copy any file from tftp to switch flash getting below timeout error.
%Error opening tftp://10.22.30.36/cat3k_caa-universalk9.16.09.06.SPA.bin (Timed out)
PER-ASW16#
However from switch flash to tftp server able to copy with block size as 8192
Conditions
On the customer environment
TFTP to switch with ip tftp block size as 8192 unable to copy the files
--We connected PC (tftp server) the 3850 on Gig 1/0/4 directly for testing.
--By default ip tftp block size 8192 and while we are trying to copy any file from tftp to switch flash getting below timeout error.
--We verified the if there is any firewall or blocking traffic, but there is no firewall.
%Error opening tftp://10.22.30.36/cat3k_caa-universalk9.16.09.06.SPA.bin (Timed out)
PER-ASW16#
--We tried different block size below 1450, which is working fine, able to copy files both ways
--Confirmed that working fine till the blocksize 1468, from 1469 onwards not working.
--Verified the system MTU confirmed that 1500
--We tried creating a test L3 VLAN and assigned IP address to that, configured as tftp source, still same issue seen.
--We did the captures and after analysis noticed last packet received on t he switch from tftp server as data sent, but no ack from switch.
Workaround
Last block size able to copy tftp to switch 3850 / running IOS 16.9.6 is 1468, from 1469 onwards issue seen
Any Other Details
--We collected the captures from customer setup and from the directly connected port to PC(TFTP Server)
Further Problem Description
PSIRT Evaluation:
The Cisco PSIRT has evaluated this issue and determined it does not meet the criteria for PSIRT ownership or involvement. This issue will be addressed via normal resolution channels.
If you believe that there is new information that would cause a change in the severity of this issue, please contact psirt@cisco.com for another evaluation.
Additional information on Cisco's security vulnerability policy can be found at the following URL:
http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html
