Maple 2021 Network Tools is supported on RHEL 7.7 and RHEL 8.0 (as well as several versions of Ubuntu and SUSE 15).
Red Hat Enterprise Linux 6 uses a different version of glibc resulting in the error:
maplelmg: /lib64/libc.so.6: version `GLIBC_2.14' not found (required by maplelmg)
when starting the server.
There are 2 ways you can install a Maple server on RHEL 6. Please note that neither of these options are supported but may work.
1. You could use Maple 18 Network Tools. The drawback to this is that this licensing is not as robust and may have trouble finding the host ID of your system. To do this you'll need to contact Maplesoft Technical Support (email@example.com). Please include in the e-mail that you're using RHEL 6 and the error received.
2. You could install glibc 2.14 on RHEL. We don't offer support on doing this and it may not be straight forward due to conflicts with glibc 2.12.