ns-allinone-2.31 Installation & Validation was correct but can't access "ns"

Hi,

I have installed "ns-allinone-2.31" and changed the PATH variables in ~/.bashrc but 'ns' command is still not working. I have checked all mails related to my problem. I also checked some other websites too but it did not help me. Please help me.

Whenever I type "ns" command in my terminal it always shows...

Usage: host [-v] [-a] [-t querytype] [options] name [server]
Listing: host [-v] [-a] [-t querytype] [options] -l zone [server]
Hostcount: host [-v] [options] -H [-D] [-E] [-G] zone
Check soa: host [-v] [options] -C zone
Addrcheck: host [-v] [options] -A host
Listing options: [-L level] [-S] [-A] [-p] [-P prefserver] [-N skipzone]
Common options: [-d] [-f|-F file] [-I chars] [-i|-n] [-q] [-Q] [-T] [-Z]
Other options: [-c class] [-e] [-m] [-o] [-r] [-R] [-s secs] [-u] [-w]
Special options: [-O srcaddr] [-j minport] [-J maxport]
Extended usage: [-x [name ...]]  server [name ...]]

I checked that alien ns by using "which ns" command and it's from "usr/bin/ns" and I can't change it. whenever I type "ns", it shows the the content above. Please help me.

Thanks.
Suranjit