DNS in two separate domain not working properly.

DNS problem
I have two separate domains.
rnet.local
roamnet.local

both are separet forest but i have setup trust between these two domains.

both domain can validate each other’s useraccount but when i try to ping by name i cannot ping while i can ping by Ip.

now i have following dns servers in rnet domain

172.16.1.239
172.16.2.239
172.16.3.239
172.16.7.239

and in roamnet

i have following DNS Servers

172.16.9.23
172.16.9.25

what i have done is from 172.16.1.239 setup a forwarder to 172.16.9.23 and from 172.16.9.23 to 172.16.1.239

now sometimes its working and sometimes its not working.

if you need any further information i can provide.
thanks