Which way -- Gateway

The gateway, I assume, can go into either of these two files.
/etc/sysconfig/network or ...
/etc/sysconfig/network-scripts/ifcfg-eth0

Why should it make a difference?
Is the only difference that the gateway should go in
/etc/sysconfig/network ...
unless you have more than one i/f with each i/f having its own gateway.
In which the gateway should be configured in
/etc/sysconfig/network-scripts/ifcfg-eth1???

I may be making some assumptions...
Can someone point me in the right direction?

Thanks!

.