AM1707 EVM nfs boot questions

   my am1707 can boot from spi flash and nand flash ,but when i boot with nfs mode ,it does't run;

   my host tftp and nfs configration is well,in my host , i am sure that i can  use 'mount' command correctly ,and i remote mount is well ,and my EVM also can ping the host.

but i don't mount my host's directer to my EVM ,i do'n know what some thing wrong !

 please help me.

 a embedded lover but don't excellent.

 i am sorry , my english is not very good ,please beg me . 

 i type the commands  list below:

host $ /usr/sbin/exportfs -av
host $ /sbin/service nfs restart
host $ /etc/init.d/iptables status
host $ /etc/init.d/iptables stop

U-Boot > setenv nfshost 192.168.1.77
U-Boot > setenv rootpath /share/target
U-Boot > setenv serverip 192.168.1.77
U-Boot > setenv bootfile uImage
U-Boot > setenv bootcmd 'dhcp;bootm'
U-Boot > setenv bootargs console=ttyS2,115200n8 noinitrd rw ip=dhcp root=/dev/nfs nfsroot=${nfshost}:${rootpath},nolock mem=32M
U-Boot > boot

this is my ubot environmetn:

U-Boot > printenv
bootdelay=3
baudrate=115200
ethaddr=00:0e:99:02:ff:87
ipaddr=192.168.1.125
stdin=serial
stdout=serial
stderr=serial
ver=U-Boot 2009.11 (Mar 16 2011 - 13:26:26)
nfshost=192.168.1.77
serverip=192.168.1.77
bootfile=uImage
bootcmd=dhcp;bootm
bootargs=console=ttyS2,115200n8 noinitrd rw ip=dhcp root=/dev/nfs nfsroot=192.168.1.77:/mount/target,nolock mem=32M
rootpath=/share/target

Environment size: 377/131068 bytes

this is my error under uboot:

U-Boot > boot   
BOOTP broadcast 1
BOOTP broadcast 2
BOOTP broadcast 3
BOOTP broadcast 4
BOOTP broadcast 5
BOOTP broadcast 6
BOOTP broadcast 7
BOOTP broadcast 8
BOOTP broadcast 9
BOOTP broadcast 10

Retry count exceeded; starting again
BOOTP broadcast 1
BOOTP broadcast 2
BOOTP broadcast 3
BOOTP broadcast 4
BOOTP broadcast 5
BOOTP broadcast 6
BOOTP broadcast 7
BOOTP broadcast 8
BOOTP broadcast 9
BOOTP broadcast 10

Retry count exceeded; starting again
BOOTP broadcast 1
BOOTP broadcast 2
BOOTP broadcast 3
BOOTP broadcast 4
BOOTP broadcast 5
BOOTP broadcast 6
BOOTP broadcast 7
BOOTP broadcast 8
BOOTP broadcast 9
BOOTP broadcast 10

Retry count exceeded; starting again
BOOTP broadcast 1
BOOTP broadcast 2
BOOTP broadcast 3
BOOTP broadcast 4
BOOTP broadcast 5
BOOTP broadcast 6
BOOTP broadcast 7
BOOTP broadcast 8
BOOTP broadcast 9
BOOTP broadcast 10

 

thank you!

sincerely ! luo....