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U-Boot Network Settings

The network settings of U-Boot can be manually set or tweaked on the fly. All of the network settings are available as U-Boot environment variables which can be changed using the standard environment commands. The environment settings can then be saved into flash and restored automatically the next time U-Boot boots.

Network Variables

Variable Meaning
ethaddr The MAC address of the Blackfin board
gatewayip The IP address for routing packets outside of the local network (as defined by the netmask)
hostname The hostname of the Blackfin board
ipaddr The IP address of the Blackfin board
netmask The Network Mask for the Blackfin board
rootpath The root path when using Linux with an NFS root file system
serverip The IP address used when running a command that needs a server (like tftp)

Showing Variables

The value of any variable can be seen at runtime by using the print command. If you do not specify the variable to print, then all variables will be shown.

bfin> print ethaddr
ethaddr=00:e0:22:fe:4f:cd
bfin> print ipaddr
ipaddr=192.168.0.15

Changing Variables

With the exception of the ethaddr variable, you can set any variable at runtime by simply using the set command.

bfin> set ipaddr 192.168.1.22
bfin> print iapddr
ipaddr=192.168.1.22

Changes take effect immediately. To put it another way, the variable settings are re-read every time a related network operation is run.

Clobbering The Unclobberable

The default behavior of preventing modification of certain variables (like ethaddr) is controlled via the CONFIG_ENV_OVERWRITE option in your board configuration file.

If you wish to get tricky, you could use the mm command to directly modify the environment wherever it lives in memory.