Please log into the DR appliance via ssh, and verify the current iDRAC network settings using this command:
maintenance --remote_access --show
If the settings are incorrect, you can set them manually like this:
maintenance --remote_access --enable --static_ip --ip 192.168.1.15 --netmask 255.255.255.0 --gateway 192.168.1.1
That's just an example; use your appropriate settings.
If the settings look correct, try resetting the iDRAC with the command:
maintenance --remote_access --racreset
Then you'll have to wait for the iDRAC to reboot before trying to access it again. You can also monitor the status while it is rebooting with the previous mentioned "maintenance --remote_access --show" command.