Multiple nic, different subnet

Question

Does multiple nic setup with different subnet in Ubuntu actually require some extra steps to work correctly? I can't seem to bind curl/any other apps to one of the nic and make it uses that nic connection.

I have 2 nic plugged to my computer, one is onboard wired nic and wireless usb adapter. Both of them are connected to different routers and are assigned with different ip range and gateway ip. Before you ask

$ ip -4 a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN 
    inet 127.0.0.1/8 scope host lo
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    inet 10.10.1.2/24 brd 10.10.1.255 scope global eth0
4: wlan1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
    inet 192.168.1.2/24 brd 192.168.1.255 scope global wlan1

$ ip -4 r
default via 10.10.1.1 dev eth0  proto static 
10.10.1.0/24 dev eth0  proto kernel  scope link  src 10.10.1.2  metric 1 
169.254.0.0/16 dev eth0  scope link  metric 1000 
192.168.1.0/24 dev wlan1  proto kernel  scope link  src 192.168.1.2  metric 2 

$ netstat -rn output
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         10.10.1.1       0.0.0.0         UG        0 0          0 eth0
10.10.1.0       0.0.0.0         255.255.255.0   U         0 0          0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 eth0
192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 wlan1

I can ping their ip/gateway fine but binding to the usb adapter always fail. So any idea how to get this to work?

Answer 1

I'm not sure about curl, but wget's man page says:

   --bind-address=ADDRESS
       When making client TCP/IP connections, bind to ADDRESS on the local
       machine.  ADDRESS may be specified as a hostname or IP address.
       This option can be useful if your machine is bound to multiple IPs.

Specify the IP address of the nic you want to use.

Answer 2

FOUND THE SOLUTION!

Turns out that I need to add a new routing table for the additional nic and then add routing rules for it in the table. Read more for instructions in this link