[ns] Can I install different versions of Network Simulator2? How can I distinguish them?

[pietro.luigi.c@alice.it]

Can I install different versions  of Network Simulator2? How can I distinguish them?

I have installed ns-2.29 on Ubuntu 8.04 Hardy Heron.

I type "which ns" and this is the output:

"/usr/local/bin/ns"

Now if I install ns2.1b8a I will have always "ns" command,
but then to which version it will be referred??

Please help me,
Thank u in advance,
Pietro