Hi All,
I have a cisco sg300 52 port switch. I have only two computers connected to two ports on vlan 1. One computer has tftp server configured and the other one has atftp client installed. The NIC of two computers are configure as 1500 mtu and the two ports on the switch are configured access port. Now I am trying to transfer a file from one computer to the other using atftp client. With the atftp client I configure the block size. When I set the block size to for example 1024 bytes, and I monitor with tcpdump on my tftp server computer I can see all packets being send and transferring file is successful. However when I specify a larger than 1500 bytes block size I see the fragmentation/reassembly in my tcpdump of the NIC. However after exactly 256 packets sends and received correctly, I see that packet 257 not being transferred . From the tcpdump it seems that the server resend packet 257 multiple times (fragmentation of this packages seems ok) but somehow the client does not seems to receive those fragmented packets anymore since I dont see an ACK of the client. At certain point the client stop the transfer by sending a "time to live" reassembly time out.
Can anyone give me a clue on what could have happened here and what to do to further investigat what went wrong ?
