Home Technology What Is An Advantage Of Using Legacy Inter-Vlan Routing – What is Legacy Inter-VLAN Routing? – Explained

What Is An Advantage Of Using Legacy Inter-Vlan Routing – What is Legacy Inter-VLAN Routing? – Explained

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Once we found that each VLAN is generally focusing on its subnet. The network switches mainly work on layer 2 from the OSI model, so they don’t check out the logical addresses. Therefore for traffic between VLAN inter-VLAN routing is needed. The Legacy Inter-VLAN routing may be the first solution for traffic between different VLAN. It depends on routers with multiple physical interfaces. All interface needed to be linKed to another network and configured having a separate subnet.

The legacy inter-VLAN routing connects different physical router interfaces to various physical ports around the switch. The switch ports attached to the router should be put into access mode.

Each physical interface from the router is owned by another VLAN and also the router interface then accepts the traffic in the VLAN related to the switch interface it’s linked to. Then your router transmits the visitors to other VLANs attached to the other interfaces. The figure below illustrates the legacy inter-VLAN routing process.


We are able to observe that host 1 is VLAN 100 and host 2 is within VLAN 200. Therefore if host 1 really wants to send data for hosting 2, the steps could be following.

  • Host – 1 on VLAN 100 is contacting Host – 2 on VLAN 200 with the Router.
  • ThE router has separate interfaces configured for VLANs.
  • Both hosts come in different VLANs, therefore have different broadcast domains and can’t send traffic directly with no default gateway.
  • Host – 1 will check its ARP cache for MAC address from the default gateway, when the MAC address can be found in the ARP cache from the host – 1, after which host – 1 will be sending the information packet towards the router. However, if the ARP cache doesn’t have MAC address from the default gateway, then your host -1 will create the ARP request the default gateway MAC address.
  • After obtaining the MAC address from the gateway the host -1 will be sending the packet to the default gateway (the router interface fa0/) Once the router receives the frame. It blogs about the destination Ip by talking about its routing table to understand that interface it ought to forward the information for the destination host.
  • The router then forwards an ARP request the interface attached to the destination VLAN once the switch receives the content, it might ton it to the ports as well as in this situation, host – 2 would reply using its MAC address.
  • Router – 1 would then make use of this information to transmit it for hosting – 2 like a unicast frame.
  • December 28, 2018


Configure Legacy Inter-VLAN Routing

Multiple Physical interfaces are needed around the router to configure Legacy inter-VLAN. The router can produce a routing with every of their physical interfaces linked to a distinctive VLAN. Configure each physical interface using the unique Ip for that subnets associated with the specific VLAN.

After configuring the Ip on physical interfaces, each device attached to the LAN can communicate towards the router by using this physical interface. The router will be the gateway for every device around the VLAN. All of the VLAN can talk to one another without configuring any routing protocol around the router.  The legacy Inter-VLAN routing needed configuration around the switch and also on the router. The figure below illustrates the Legacy inter-VLAN routing:


Legacy Inter-VLAN Routing – Switch Configuration

To configure legacy inter-VLAN routing starts by configuring the switch. As proven within the figure, the Router is linked to switch ports Fa0/2 and Fa0/7, that have been configured for VLANs 100 and 200, accordingly.

Make use of the following command to produce VLAN and assign ports to that particular VLAN. Keep in mind that issue the command in global configuration mode. The main harbour should be in access mode.

Within this example, the interfaces Fa0/1 to Fa05 happen to be allotted to VLAN-100 and also the interfaces Fa0/6  to Interfaces Fa /10 happen to be allotted to VLAN 200. While using name command have assigned the name to VLANs and lastly while using wr (write) command save the job in to the startup configuration file.

We’ve used the command “do wr” because we’re in global configuration mode. The command is initially not using in global configuration mode. So, as in “User Fortunate Mode” only then do we would make use of the command “wr or write”. We are able to also employ the copy “running-config startup-config” rather from the “wr” command. Watch the next video for Legacy Inter-VLAN routing configuration:


Legacy Inter-VLAN Routing – Router Configuration

Within the Legacy Inter-VLAN routing, there aren’t any static or dynamic protocols required for the routing. We’re just needed to configured the IP addresses from the router based on the subnet from the connected VLANs. We are able to configure the Ip from the interface using “IP address <ip address subnet mask> command in global configuration mode. Keep in mind that the switch should be within the status of “no shutdown”.

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