Lab 11.2 with NetworkManager ( Centos7)
If on Centos 7 with a wireless connection and NetworkManager.service ( not network.service) the format of /etc/sysconfig/network-scripts/route-< wireless-connection-name > file will be
GATEWAY0=< ADDR-Y >
and it also modifies ifcfg- < wireless-connection-name > in same location.
Notable thing is the file will have connection name instead of interface name.
Have attached the screenshot of nmtui for reference which edits /create network-scripts.