Running U-boot from RAM

[luspa]

I'm trying to follow this wiki page: http://www.plugcomputer.org/plugwiki/index.php/Re-building_the_kernel_and_U-Boot
I'd like to test the u-boot before writing to nand; the wiki says:

 
setenv serverip 192.168.***.***
setenv ipaddr 192.168.***.***
tftp 0x6400000 u-boot.kwb
go 0x0c100000

This is not working for me.
My questions are:
1. Shouldn't the 2 addresses (tftp and go commands) be the same? (I tried to change them but without success)
2. Is the u-boot binary image for running from RAM the same as the one for flashing the nand?
3. Do I have to use the u-boot.kwb OR u-boot.img file?

Thank you for any help

[marcus]

1. Shouldn't the 2 addresses (tftp and go commands) be the same? (I tried to change them but without success)

serverip is the ip address of the tftp server
ipaddr is the ip address of the sheevaplug, for U-Boot to use whilst it is being a TFTP client.

[luspa]

serverip is the ip address of the tftp server
ipaddr is the ip address of the sheevaplug, for U-Boot to use whilst it is being a TFTP client.

Thamk you for your answer but sorry, I wasn't clear enough. I meant the memory addresses of the last two u-boot commands.