SVI and VLAN Addressing Issues

/ /

Each VLAN in the network requires a unique IP subnet because two devices in the same VLAN with different subnet addresses cannot communicate. This is a common problem during VLAN configuration, and we can solve it by identifying the incorrect IP address configuration and changing the address to the correct one.

For example, if you want to connect a client anywhere in VLAN 10, you must require a valid subnet configuration. If you want to communicate outside the VLAN, you must require a valid default gateway. The default gateway must be the VLAN 10 SVI address. In the figure below, PC-2 cannot connect to PC-3 and PC-4, but PC-3 and PC-4 can communicate with each other.

IP Addressing Issue with VLANs

A check of the IP configuration settings of PC-2 shown in figure-2 Reveals the most common error in configuring VLANs a wrongly configured IP address. PC-2 is configured with an IP address of 192.178.20.1, but it should have been configured with 192.168.20.1.

ip address configuration

Solution

Change the PC-2 IP address to the correct IP address, 192.168.20.1. The PC-2 Ethernet configuration now shows the updated IP address of 192.168.10.1. The Figure below illustrates the output on the bottom and reveals that PC-2 has regained connectivity to the Web server found at IP address 192.168.20.1.

SVI Configuration

SVI stands for Switched Virtual Interface. It is a routed interface in IOS that represents the IP addressing space for a VLAN connected to it. Since the VLAN has no physical interface, the SVI provides Layer 3 processing for packets from all switch ports associated with the VLAN.

With this interface, the switch uses virtual layer 3 interfaces to route traffic to another layer 3 interface, which eliminates the need for the physical router. For virtual interface configuration, ensure your switch has a VLAN represented by the SVI you want to create. The command is the following:

WP Table Builder