Can't install glibc.i686 on RHEL7.x

I am trying to build an old piece of software which requires glibc.686. I can't seem to find where the repository is for glibc.i686.

[root@dub-001948-VM01 ~]# yum install glibc.i686
Loaded plugins: auto-update-debuginfo, langpacks, search-disabled-repos
No package glibc.i686 available.
Error: Nothing to do
[root@dub-001948-VM01 ~]#

The compiler error is:

x86.el5.i386/usr/bin/g++: /lib/ld-linux.so.2: bad ELF interpreter: No such file or directory

I have also tried to install compatibility libraries.