- Inter VLAN routing means communication between different VLANs.
- We know that communication between VLANs is not possible at layer 2.
- If we want different VLANs to communicate with each other, we want layer 3 concept.
- This is why we call Inter VLAN communication – Inter VLAN routing.
- From the 1st method we observe that for every VLAN we have to connect a physical link to router to perform IVR. It is difficult when there are many VLANs.
- So they come up with the 2nd method Router on a stick.
- To support ISL or 802.1q routing on a fast Ethernet interface, the router’s interface is divided into logical interfaces – one for each VLAN – as shown in the figure.
- These are called sub interfaces.
- You can set the interface to trunk with the encapsulation command.
- In the 2nd method also there are some limitations (Bottle neck), to overcome that we have to use a gigabit Ethernet port for IVR.
- This limitation is overcome in 3rd method. (IVR using MLS)
In this method IVR is done by using layer 3 switch, by enabling ip routing on it.
Network Lessons 