There are two possible ways for adding a default gateway. Option 1: You can add a gateway definition to  the /etc/sysconfig/network file. This definition will apply to all network interfaces. Let’s say that your gateway is 192.168.4.1,  then you need to add the following line to /etc/sysconfig/network file. GATEWAY=192.168.4.1 Option 2: You can define a [...]

After doing a kernel upgrade, default kernel configuration in GRUB config will be automatically update. On Redhat based systems you can change this behavior by modifying /etc/sysconfig/kernel file. You need to set the UPDATEDEFAULT to no. UPDATEDEFAULT=no store