Question: how to enable kdump in rhel 6?
Answer: Make sure /var/crash has space for vmcores. ... 
Add crashkernel=128M to your kernel command line in /boot/grub/grub.conf.
Setup /etc/kdump. ... 
Make sure the kdump service is set to start on boot and restart the system.
Check that there is an initrd in /boot created for kdump. ... 
Test your configuration.