Not able to access applications through Admin ser

Hi, 
we are using weblogic 8.1, 

admin server having one cluster that cluster having only one manage server, 

all the applications are deployed in Manager server not in admin server, i am
able to access the admin server through the t3://admin server name :admin server
port, 

after i am getting the initial context, i am looking up for the application JNDI
name, but the system is telling, the JNDI not available in Admin server. 

but if try to contact the manager server
t3://manager server name : manager server port, 

i am gettting the communication error like, not reachable and router is not
available.

as per my observation, if we contact the admin server the admin server will
respond to us about the applications deployed in the cluster machines, 

but why it is not happening here, is there are any errror in the cluster
configuration.

or any error in the way i am trying.

please give your suggestion. 

Thanks
Sundaravel N