routing table and (iproute2 vs net-tools)

Question

I have the following routing table:

# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.42.129  0.0.0.0         UG    0      0        0 enx6a58445c5d43
169.254.0.0     0.0.0.0         255.255.0.0     U     1000   0        0 enx6a58445c5d43
192.168.42.0    0.0.0.0         255.255.255.0   U     0      0        0 enx6a58445c5d43
192.168.57.0    0.0.0.0         255.255.255.0   U     0      0        0 vboxnet1

When I use the following command I get error:

# ip route add 192.168.42.0/24 via  192.168.57.1 dev vboxnet1
RTNETLINK answers: File exists

But When I use from net-tools I don't get any error:

# route add -net 192.168.42.0/24 gw   192.168.57.1 dev vboxnet1
# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.42.129  0.0.0.0         UG    0      0        0 enx6a58445c5d43
169.254.0.0     0.0.0.0         255.255.0.0     U     1000   0        0 enx6a58445c5d43
192.168.42.0    192.168.57.1    255.255.255.0   UG    0      0        0 vboxnet1 ####add here
192.168.42.0    0.0.0.0         255.255.255.0   U     0      0        0 enx6a58445c5d43
192.168.57.0    0.0.0.0         255.255.255.0   U     0      0        0 vboxnet1

Question is : How can I add by iproute2?

Answer 1

You have network address 192.168.42.0/24 in your routing table. So you have to:

ip route replace 192.168.42.0/24 via 192.168.57.1 dev vboxnet1 

Or

ip route del 192.168.42.0/24 
ip route add 192.168.42.0/24 via 192.168.57.1 dev vboxnet1