[CentOS] tftpd server S not responding

[Steven Tardy]

Early in this thread you mentioned these are on different network subnets.
. .

Just thought about a similar issue. . .
  sysctl -a | grep rp_filter

If a packet comes in to Linux and the path BACK to the remote IP is NOT out
that same interface (asymmetric routing) the Linux kernel will drop the
packet. “rp_filter” controls how Linux behaves regarding this.

Please provide real `ifconfig` and `route -rn` and `tcpdump port 69` output
to properly diagnose. . .