Reverse DNS and single IP address space

[James Earl]

I'm in the process of setting up primary and secondary name servers.  
This is my first time setting up named so I'm kinda a newbie in this 
area.

My question is in regards to in-addr.arpa entries in named.conf and 
zone files.  In the FreeBSD Handbook and alot of other resources, I've 
noticed how the ip address is reversed, with part of the address left 
off.  For example:

zone "0.168.192.in-addr.arpa" {
	type slave;
	file "s/0.168.192.in-addr.arpa.bak";
	masters {
		192.168.1.1;
	};
};

Now, what happens when I have only been allocated a single ip address 
from my ISP (well, actually two, one for the primary/master and one for 
the secondary/slave)?  Would I set it up like this:

zone "1.0.168.192.in-addr.arpa" {
	type slave;
	file "s/1.0.168.192.in-addr.arpa.bak";
	masters {
		192.168.1.1;
	};
};

Or, do I even need to worry about reverse DNS entries since my ISP 
already has them setup?

Thanks.