There is no specific command on CentOS to set the default route or gateway, there are several ways to do this on CentOS (as there often are). The method I am showing you will work on all versions of CentOS with or without a GUI and involves directly editing the network configuration file using Vim.
Setting default gateway on CentOS first requires us to open /etc/sysconfig/network config file using Vim:
$ vim /etc/sysconfig/network
You now need to add your default GW, if you don’t know the IP of your default GW (aka default route) then you need to ask your ISP / web host or network admin. The example below assumes our default GW is 192.168.0.1
I always append this information to the bottom on the network config file on CentOS.
After adding the default route (GW) you need to restart the networking service using:
# service networking restart