There are two common ways to connect two routers together.
The Edge router refers to the router connected to the Internet, the Slave router refers to the second router.
1. Cascade the routers
This is when the WAN port of the Slave router is connected to one of the switch ports on the Edge router. In this case, DHCP should be enabled on both routers as two network segments have been created. One segment represented by the switch on the Edge router, and the second by the switch on the Slave router.
The Slave router will obtain an address from the DHCP server on the Edge router. Devices connected to the Slave router will receive their IP addresses from it.
Advantages: Allows you to use all of the switch ports on the slave router; creates a security barrier between the two network segments;
Disadvantages: Limits communications between devices on the two segments (file and printer sharing may not be possible); All traffic from devices connected to the Slave router are translated twice before reaching the Internet (this extra overhead may slow down the performance of things like gaming);
2. Cascade the switches.
This is when one of the switch ports of the Slave router are connected to one of the switch ports on the Edge router. In this case, DHCP should be disabled on the Slave router. This configuration provides one logical network segment shared across both switches.
If the Slave router is being used as more than just a switch (a wireless router), it will need to be given an IP address in the same network as the DHCP server on the Edge router.
Advantages: There is only one network segment so file/printer sharing will work fine; Network addresses are only translated once (by the Edge router) so there is less overhead for devices connected to the Slave router;
Disadvantages: One switch port on each router is used to link the two devices; A crossover cable may be required to connect the two switches; If the Slave router is a used for VOIP, this configuration may not allow the VOIP functions to work;
If all you need are extra ports for other devices, buy a cheap switch or hub, it will save you some grief! If you need to create a security barrier between devices on your networ, use a second router, or the DMZ function available in some routers.
It's not the heat, it's the humility!