Needing to reboot after adding/removing same gateway route

As a matter of study I'm using VirtualBox with Debian 8 to learn basics of networking with the interface in bridge mode. I deactivated dhcp of my network interface eth0 on /etc/network/interfaces: # ... # iface eth0 inet manual Now I'm configuring the interface by my own: # ifconfig eth0 192.168.0.99/24 And then, I test my gateway (which is 192.168.0.1) with ping and it works perfectly. Then I add the default gateway to my routes table: # route add default gateway 192.168.0.1 netmask 255.255.255.0 dev eth0 After some tests, downloads, etc. I see that everything is OK. Then decided to learn how to delete routes and tested it with my default gateway. It works. ### Here is my problem After trying to add my gateway again with the same line above I got the "**SIOCADDRT: Network is unreachable**" error. ### What I tried to solve? 1. ifdown and ifup my interface; 2. Reconfigure the interface with ifconfig; 3. Restarting the networking daemon. The only thing that works is **restarting** the machine. **Is there a way to add my route again without the need of restarting the machine?**