[syslinux] PXE boot hangs while transferring vmlinuz or initrd.img

[Michael Madore]

Hi,

I have a user that is experiencing problems pxe booting several
identical servers.  pxelinux.0 is from syslinux 3.63 and the TFTP
server is 0.42 running on CentOS 5.2.

After loading pxelinux.0, the client will then start transferring
vmlinuz and initrd.img via tftp.  More than half the time, the
transfer will get stuck and then eventually print a timeout message.
I ran tcpdump and I can see that the server stops sending data
packets.  The client keeps sending the last ACK until it times out:

No.     Time        Source                Destination           Protocol Info
   2456 62.303446   10.4.253.5            10.4.253.206          TFTP
  Data Packet, Block: 1185
   2457 62.303768   10.4.253.206          10.4.253.5            TFTP
  Acknowledgement, Block: 1185
   2458 62.303782   10.4.253.5            10.4.253.206          TFTP
  Data Packet, Block: 1186
   2459 62.304105   10.4.253.206          10.4.253.5            TFTP
  Acknowledgement, Block: 1186
   2460 62.304120   10.4.253.5            10.4.253.206          TFTP
  Data Packet, Block: 1187
   2461 62.307321   10.4.253.206          10.4.253.5            TFTP
  Acknowledgement, Block: 1187
   2462 65.561489   10.4.253.206          10.4.253.5            TFTP
  Acknowledgement, Block: 1187
   2463 72.152335   10.4.253.206          10.4.253.5            TFTP
  Acknowledgement, Block: 1187

It appears to get stuck in a random location in either vmlinuz or
initrd.img.  The strange thing is that this only happens when booting
the kernel and ramdisk from CentOS 5.2.  Booting the kernel and
ramdisk from CentOS 4 works.

Any suggestions for debugging this further?

Thanks,

Mike Madore