i have two gateways for single route 
Ex.

```
destination 172.20.100.4  gateways 10.22.0.9 and 10.192.168.18

```

I want to add both routes in my route add if one is fail traffic goes automatically from other source. 

```
route add 172.20.100.4 mask 255.255.255.255 10.22.0.9 
route add 172.20.100.4 mask 255.255.255.255 10.192.168.18 

```

what metric do I install for both routes and both IP addresses for single Ethernet..