RedHat 8

I am makeing an NFS on a secondary comp.

I have the required line in the /etc/exports file
I have started the NFS service

I try to mount the shared file on THIS computer:

mount tim2:/shared / (i want it in the / directory)

but it says: can't get address for tim2 (tim2 is the hostname of the NFS server comp)

if i put IP addy in instead it says:
Port mapper failure - RPC: Unable to receive

i cant mount it for some reason. i have been working on this for hours, can anyone help me?

on the machine with the nfs server, did you type in as root

exportfs -a

and for tim2, is it listed in the othercomptures /etc/hosts file? or listed with a dns server