Passing Your CCNA and CCNP: Configuring And Troubleshooting Router-On-A-Stick
For CCNA and CCNP candidates, it’s hard not to laugh the first time you hear the phrase “router on a stick”. Let’s face it, that’s a pretty silly term. But as those who have passed the CCNA and CCNP exams know, this is a vital exam topic that you must know how to configure and troubleshoot.
Basic Cisco theory states that for hosts in different VLANs to communicate, a Layer 3 device must be involved to handle the routing between the VLANs. That device is a router, and there are special considerations that must be taken into account for both the physical router itself and the configuration you’ll be writing.
The router will be connected to a switch via a FastEthernet port (or higher). The router port cannot be a regular Ethernet port, since the router port will need the ability to send and receive data at the same time.
The configuration of the interface is where things get interesting. Let’s say we have two VLANs that will be using router-on-a-stick to communicate.
Here is the VLAN information:
VLAN 20: ...