This problem happens ussually when the workstation running CCA does not point to the UC500 as its default gateway. We often just add a route ("c:\>route add 192.168.0.78 mask 255.255.255.0 192.168.10.1" for instance) on the workstation to correct the problem. A UC540 ussually has this line in its running configuration file, "ip tftp source-interface Loopback0". So another method that we do try is removing that command. In a CCA compliant configuration the Loopback0 IP address is 10.1.10.2.
Found. It's one of my stupid mistakes. Sometime happen. Too much. The problem is firewall enabled on PC. A classic warning on manuals . Only one mitigation factor: normally I work with workstation with firewall disabled.
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