There are two net cards in used status in my pc.

```
ifconfig

eth0      Link encap:Ethernet  HWaddr e0:3f:49:57:4b:d1
          inet addr:192.168.1.3  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::e23f:49ff:fe57:4bd1/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:6068 errors:0 dropped:0 overruns:0 frame:0
          TX packets:113 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:3780468 (3.6 MiB)  TX bytes:11800 (11.5 KiB)

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:14 errors:0 dropped:0 overruns:0 frame:0
          TX packets:14 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:700 (700.0 B)  TX bytes:700 (700.0 B)

wlan0     Link encap:Ethernet  HWaddr 00:21:5d:26:c1:10
          inet addr:192.168.1.101  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::221:5dff:fe26:c110/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1291 errors:0 dropped:0 overruns:0 frame:0
          TX packets:5146 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:81917 (79.9 KiB)  TX bytes:992000 (968.7 KiB)

```

How to know which ip address is used when to connect to yahoo.com with my pc?