SSH client times out after 5 minutes (RHEL 6.6)

I’m stumped with an issue that I hope someone can point me in the right direction. SSH sessions keep timing out after 5 minutes on a RHEL 6.6 system. ClientInterval is set to 900, ClientAliveCountMax is set to 0. I have checked the TMOUT variable and it is set to 900. TCPKeepAlive is set to yes but is commented out. Even uncommented it is still dropping at 5 minutes. I'm not sure where else to look. A co-worker mentioned that it was compiled in the kernel but I have done a kernel upgrade to 2.6.32-642.3.1.el6.x86_64 from Red Hat and it still exists.

Any help or guidance is appreciated.

Thanks
Robert