How to correctly use 2 on board nics

[Ivan Carey]

Hello
I have a server board with 2 onboard nic's
I have set them up in rc.conf as follows

defaultrouter="192.168.1.1"
network_interfaces="em0 em1 lo0"
ifconfig_em0="inet 192.168.1.3 netmask 255.255.255.0"
ifconfig_em1="inet 192.168.1.4 netmask 255.255.255.0"

The question, is this the correct configuration?

If I have both nic's connected to the switch I can ping 192.168.1.1 and 
192.168.1.3 and 192.168.1.4

If I have only em0 connected I can ping 192.168.1.1 and 192.168.1.3

If I have only em1 connected I can ping 192.168.1.3.

What could the 2 onboard nic's be best used for. I was thinking that in 
the event on was to fail then the other would still be ok.

Any ideas would help.
Thanks,
Ivan