Type this to the terminal
cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0:0

Change the values to your desired IP address which is in different subnet.

It should look like this

[root@choi ~]# ifconfig
eth0 Link encap:Ethernet HWaddr 00:0C:29:FD:78:BE
inet addr:192.168.0.100 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fefd:78be/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:469 errors:0 dropped:0 overruns:0 frame:0
TX packets:534 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:43223 (42.2 KiB) TX bytes:100665 (98.3 KiB)
Base address:0x1070 Memory:e8820000-e8840000

eth0:0 Link encap:Ethernet HWaddr 00:0C:29:FD:78:BE
inet addr:192.168.2.101 Bcast:192.168.2.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Base address:0x1070 Memory:e8820000-e8840000