FTP problem

I recently had to change a router and this has caused a variety of problems.

I changed the RDB entries on a V5R1 server to reflect a new internal IP
address for a V5R2 server on the same network, but when I execute the
command STRTCPFTP on the V5R1 server and enter the RDB name for the V5R2
server, I get

TCP101A - cannot find 'myhostname'.

Yet I can ping the internal address stored in the RDB definition for the
V5R2 server without problem, both from Windows and using the ping command
on the V5R1 machine.

I wonder (ignorantly!) if the problem is with the router configuration
(which I didn't set up).

All help gratefully received.

many thanks

Rob Dixon