linux 设置默认网关与网卡ip不同网段

a.b.c.d is the host IP
e.f.g.h is the gateway IP
a.b.c.d & e.f.g.h are on different subnets.
by default if you try to set gateway by following command :

route add default gw e.f.g.h

you will get this error :

SIOCADDRT: No such process

the trick is simple , first add a route to default gateway itself and then set the default gateway , like this :

route add e.f.g.h/32 dev eth0
route add default gw e.f.g.h

remember you may need to change eth0 to your device name , it may be eth1 or wlan0 or anything.

How to make these route changes persistent ?

For Debian/Ubuntu :
Add the following lines to /etc/network/interfaces :

post-up route add e.f.g.h/32 dev eth0
post-up route add default gw e.f.g.h