I have a 2811 router at a remote location. The router's Ethernet port has 3 subinterfaces, - the main interface is unnumbered but 0/0.1, 0/0.2 and 0/0.3 are numbered and are using dot1q encapsulation. If I do a ping command I have to do the extended ping and choose what interface I want to use. That has been working for me but now I need to copy the config to a ftp server but it is not working. I believe it is similar to the ping problem because it doesn't know what interface to use but I can't specify what interface to use in a copy command. Am I overlooking something really simple? The VLAN 1 interface is tagged as native. Thanks.
Just to be clear, are you talking about tftp or ftp because you mention ftp in your message.
Assuming tftp try this command
ip tftp source-interface "interface"