Unable to deny remote access to Postgresql even if there is no entry in pg_hba.conf I have 5 Postgres Servers, with IP addresses let's say as A,B,C,D and E.
A is the master server and remaining are the child servers which need to access A. In the postgresql.conf file of A, the listen address has been set to '*'. 

Now, let's say I want B to access A remotely. For that, the pg_hba.conf file of A should contain an entry with the IP address of B (along with other necessary data), like this for example:

host all    all     IP_Address_of_B 32    md5


But, the problem which I am facing is that even if I am entering the details of any one of the child servers in the pg_hba.conf file of A, the access to A is enabled to all of the child servers. And if I remove that entry, then the access is disabled for all.

As far as I know, if the entry of B is present in the pg_hba.conf file of A, the only B must be allowed to access A, not the remaining. But, in my case, either all have the access or none.

Is their a way to enable only B (or only a selected servers, not all) to access A ?
The IP address should be followed by either a slash and a mask length (like /32) with no whitespace, or by whitespace and a netmask (like 255.255.255.255).  What you seem to have here is whitespace and mask length.  So you get a mask length being interpreted as a netmask.  I am surprised that that doesn't throw an error upon parsing, but in any event it doesn't do what you want.