RHEL6: "RTNETLINK answers: No such process" even although subnet of router is defined

Issue

• I need to add the route to the 10.20.1.0 network. As you can see routes to gateway 10.1.10.12 already exist. Below is the list of routes to router 10.1.10.12 on the 10.1.10.x network.

10.20.1.2      10.1.10.12      255.255.255.255 UGH   0      0        0 eth7
10.20.1.21     10.1.10.12      255.255.255.255 UGH   0      0        0 eth7
10.1.10.0       0.0.0.0         255.255.255.0   U     0      0        0 eth7

• But the following error is returned:

# ip route add 10.20.1.0/24 via 10.1.10.12 dev eth7
RTNETLINK answers: No such process