NFS Problem

Dear sir

i am using NFS server , instead of using the domain names i am using the IP addresses of my clients machines
the file /etc/export looks like

/google 203.215.160.2(rw)
/345 203.215.160.2(rw)
/mnt/cdrom 203.215.160.2(rw)

now when i mount the directories on my client machine it get mounted okay and i can read any file in the mounted directories but as above i have given the write permision as well ,but i cant write any thing and this message show * permission denied*.

waiting for response plz .

regards

Muhammad Sibtain