Lets look at this.

/ 192.168.1.0/24(rw)

This seems sane, you are wanting to export the entire filesystem to any host in the 192.168.1.*/24 subnet.
However it seems a bit insecure by opening the entire filesystem to the world, Please make an entry for each directory that you wish to export and use the first usable address of the chosen domain to make it cleaner, such as:

/tmp 192.168.1.1/24(rw)

Now lets look at the fstab.

192.168.1.100:/tmp      /home/backup1      nfs     intr

Have to tried adding the syncronization, secure port options, inode access updates, the nfs server type and the readable/writable flags?

192.168.1.100:/tmp      /home/backup1      nfs     rw,intr,hard,nfsvers=3,noatime,secure,sync   0     0