Hello Sir,

I have installed gcc41-compat-4.1.2-ubuntu1210_i386.deb and g++41-compat-4.1.2_i386.deb and then reboot. After that I have done following:

1) tar xvf ns-allinone-2.28.tar.gz
2) patch -p0 < ns-2.28-gcc410.patch.txt
3) export CC=gcc41 CXX=g++41
4) cd ns-allinone-2.28/
5) ./install
Then I got this error: * Build tcl8.4.5
============================================================
loading cache ./config.cache
checking whether to use symlinks for manpages... no
checking compression for manpages... no
checking for gcc... gcc41
checking whether the C compiler (gcc41 ) works... no
configure: error: installation or configuration problem: C compiler cannot create executables.
tcl8.3.2 configuration failed! Exiting ...
Tcl is not part of the ns project. Please see www.Scriptics.com
to see if they have a fix for your platform.

Please help me.

May be you have a 64bits OS ? ( NS2 is for 32bits, i686.)
This command will show if the architecture is i686 or x86_64 :
$ uname -m


Also : Seems you forgot the patch (2) ns228-gcc40.patch, i.e. both patches must be used.
1) tar xvf ns-allinone-2.28.tar.gz
2) patch -p0 < ns228-gcc40.patch
3) patch -p0 < ns-2.28-gcc410.patch <Enter> <Enter> <Enter>
4) export CC=gcc41 CXX=g++41
... If you really did this wrong, please delete everything, and start from scratch.

.