Muftasoft TM

This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong.
**Inter-VLAN routing** and explore how to configure subinterfaces on router interfaces. This is a crucial topic for network administrators, especially when dealing with segmented LANs. 🌐🔌

### **What is Inter-VLAN Routing?**
- **Inter-VLAN routing** allows us to logically segment a Local Area Network (LAN) into different broadcast domains using **Virtual Local Area Networks (VLANs)**.
- Each VLAN acts as a separate broadcast domain, enhancing security, simplicity, and flexibility.
- However, for communication between VLANs, we need a routing device (usually a router or Layer 3 switch).

### **Methods of Inter-VLAN Routing:**
1. **Traditional Inter-VLAN Routing:**
    - In this method, we use a router with **multiple physical interfaces**.
    - Each interface connects to a switch, with one interface per VLAN.
    - The switch ports connected to the router are set to **access mode**.
    - Each router interface becomes the **default gateway** for hosts in its associated VLAN.
    - When hosts from different VLANs need to communicate, traffic is routed through the router.
    - ![Traditional Inter-VLAN Routing](https://www.comparitech.com/wp-content/uploads/2023/12/Traditional-Inter-VLAN-Routing.png)
    - Example: If **Host A** (VLAN 10) wants to send a message to **Host B** (VLAN 20):
        1. Host A checks if the destination IP is in its VLAN.
        2. If not, it forwards the traffic to its default gateway (router interface Fa0/0).
        3. Host A sends an ARP request to the switch to find the router's MAC address.
        4. The frame is unicast to the router, which then routes it to VLAN 20.
    - Each router interface handles traffic for its connected VLANs.

2. **Router-on-a-Stick Inter-VLAN Routing:**
    - In this approach, we use a single router interface (usually a **subinterface**).
    - The router interface connects to a trunk port on a switch.
    - The trunk carries traffic for multiple VLANs.
    - The router processes VLAN-tagged frames and routes between VLANs.
    - ![Router-on-a-Stick Inter-VLAN Routing](https://www.comparitech.com/wp-content/uploads/2023/12/Router-on-a-Stick-Inter-VLAN-Routing.png)
    - Example: Configure a subinterface on the router (e.g., **ge-0/0.10** for VLAN 10 and **ge-0/0.20** for VLAN 20).
    - The router's IP addresses on these subinterfaces serve as default gateways for hosts in their respective VLANs.

3. **Multilayer Switch Inter-VLAN Routing:**
    - Multilayer switches (Layer 3 switches) can perform inter-VLAN routing.
    - They have VLAN interfaces and routing capabilities.
    - Each VLAN has an associated SVI (Switch Virtual Interface).
    - The switch routes traffic between VLANs internally.
    - ![Multilayer Switch Inter-VLAN Routing](https://www.comparitech.com/wp-content/uploads/2023/12/Multilayer-Switch-Inter-VLAN-Routing.png)
    - Example: Configure SVIs for VLAN 10 and VLAN 20 on the multilayer switch.
    - The switch handles inter-VLAN routing without an external router.

### **Configuration Steps:**
1. **Traditional Inter-VLAN Routing:**
    - Connect router interfaces to switch ports (access mode).
    - Assign IP addresses to router interfaces.
    - Set each router interface as the default gateway for its VLAN.

2. **Router-on-a-Stick Inter-VLAN Routing:**
    - Configure subinterfaces on the router.
    - Assign IP addresses to subinterfaces.
    - Set the router's IP addresses as default gateways for VLANs.

3. **Multilayer Switch Inter-VLAN Routing:**
    - Configure SVIs on the multilayer switch.
    - Assign IP addresses to SVIs.
    - Enable routing on the switch.

Remember, the choice of method depends on your network design and requirements. Happy routing! 🌐🚀