[ns] Help with ns2.28 install on 64 bits machine using redhat enterprise linux 4

[zhihua wen]

Our lab has just bought a 64 bits zeon machine from dell with redhat =
enterprise linux 4.
I have tried to install ns2.28 all in one on it. The installation failed =
at otcl 1.9 as follows:
Build OTcl-1.9
Continuing with default options...
checking build system type... Invalid configuration =
`x86_64-unknown-linux-gnu': machine `x86_64-unknown' not recognized
configure: error: /bin/sh ./config.sub x86_64-unknown-linux-gnu failed
otcl-1.9 configuration failed! Exiting ...
Please check http://www.isi.edu/nsnam/ns/ns-problems.html
for common problems and bug fixes.

Does anyone has similar experiences? Is it because 64 bits or the =
version of linux or gcc? Thanks very much for sharing.