Sub-interfaces can also be created under a single physical interface of the router to hold the IP addresses of each VLAN. With the router configuration, all inter VLAN connections are handled either by a single physical router interface (“router-on-a-stick”), or multiple physical interfaces. Having VLANs on a network simply means each VLAN is a different network segment with a different network address subnet.Īlthough inter VLAN communication can be achieved using a router with multiple interfaces, SVIs come with less complexities. SWITCH(config-if)# ip address 10.0.1.1 255.255.255.0 <- assign IP to the SVI The need for SVIs SWITCH(config)# interface vlan 20 <- now create the SVI for VLAN 20 SWITCH(config)# vlan 20 <- create Layer 2 VLAN 20 The following commands are the same as above for creating SVI for VLAN 20. Two SVIs are created for the Workstations and Server VLANS as shown in the configuration example here. The last line assigns an IP address on the SVI created for VLAN 10 – in this case. Although the third line is OPTIONAL, it is recommended that you add an interface description, which will assist in understanding the purpose of the SVI. The following line creates an SVI for VLAN 10 (i.e the Layer3 interface). The first line in the example above creates the layer 2 VLAN 10. SWITCH(config-if)# description WORKSTATIONS SWITCH(config)# interface vlan 10 <- now create the SVI for VLAN 10 SWITCH(config)# vlan 10 <- first create the Layer2 VLAN 10
#CISCO IOS DEFINITION HOW TO#
The configuration example shown below assumes that you already know how to carry out basic switch configuration such as changing hostnames, going to global configuration mode, interface configuration mode, and assigning IP address on an interface. Keep in mind that the switch has to be a layer 3 switch, in order for this to be achieved. Now let’s see a brief configuration example for creating two SVIs on a layer 3 switch based on the network diagram above.
![cisco ios definition cisco ios definition](https://www.cisco.com/c/dam/en/us/support/docs/security/ios-intrusion-prevention-system-ips/105627-sdm-ios-ips-config-13.gif)
This implies that an IP address can be assigned to this interface for the purpose of management. This means also clients that are connected to that VLAN will make use of the SVI interface as their default gateway.Ī default SVI is created on the layer 3 switches for VLAN 1 (default native vlan), which is meant for remote management of switches. The major difference here is that the SVI Layer 3 interface is virtual. You start by creating the Layer 2 VLAN on the switch, and then assign an IP address on the VLAN Layer3 interface (SVI), just as you would on a physical router interface. Since each VLAN is an isolated network segment of it’s own, layer 3 switches need to be configured in such a way to allow inter VLAN communication. Then, for each Layer2 vlan you need to create a corresponding Layer3 interface on the switch which will handle the routing functionality. In order for this goal to be achieved using Layer 3 switches, multiple Layer 2 VLANs are created on the switch, which separates everything into multiple broadcast domains.
![cisco ios definition cisco ios definition](https://www.tech-faq.com/wp-content/uploads/Cisco-ios1.jpg)
![cisco ios definition cisco ios definition](https://www.cisco.com/c/dam/en/us/support/docs/ios-nx-os-software/ios-software-releases-110/13178-15-b.gif)
Using a router for network segmentation means each interface on the router becomes a network segment of its own, or what is known as a separate broadcast domain. This brings the need for network segmentation and inter-vlan communication, which can be achieved by using a router or a Layer 3 switch. However, devices that are not on the same VLAN cannot communicate with each other without some form of routing implemented. Layer 2 VLANs create what is known as a single broadcast domain, which simply means that when a broadcast message is sent within the same Layer2 VLAN, all the devices connected to that vlan (either on the same or separate switches) will receive the message.Īlso, hosts connected in the same Layer 2 vlan can communicate with each other without any Layer 3 device required. Local Area Network (LAN) communication deals with switches, while internetwork connectivity (i.e between different LANs or WANs) requires the use of a router. The basic purpose of creating a computer network is to share resources and offer communication between hosts. Achieving convergence in computer networks is something that is controlled by both routers and switches in the network.