Inter-VLAN routing vs. Standard routing

[azi123]

Hi, everybody!

I'm admin of a LAN and now I'm supposed to configure routing on it.

I can define some VLANs on the network and also configure inter-VLAN routing between them(by SVIs or router on a stick). But when I associate each VLAN a subnet, what is the necessity of defining VLANs? Without VLANs, there are some subnets and I configure standard routing, like OSPF, between them and subnets, are separated from each other(like VLANs). So I can't recognize whether to use VLAN-based design or another. Could you please help me with this?

Best, Amir

[Georg Pauwen]

Hello,

I don't understand your question to be honest. If you need separate subnets, you either use SVIs (VLAN interfaces), or physical (sub) interfaces, as you have mentioned. If all are configured on the same device, you don't need any routing protocol.

What does your network look like ?

[Dennis Mink]

can you add a picture of your network including subnets. if you have a faitrly flat network, you might get away with intervlan routing. cheers

[jalejand]

Hi Azi

It would be necessary to know which devices and topology you are running in order to fully understand what are you trying to achieve. Whenever you do inter-vlan routing, it means that you are using standard routing as well. For example, from all the VLANs connected to a particular core switch, inter vlan routing can be done with SVIs by creating a layer 3 interface that belongs to a particular broadcast domain, as these interfaces are considered "Connected" interface from the RIB perspective, routing is being done via connected interfaces.

For remote networks you might start using Dynamic routing protocols as you are no longer dealing with VLANs.

For example:
Inter-vlan routing can be done between VLANs to one site (Vlan 10, 20 and 30 running on the LAN), in summary, to communicate VLANs within one local LAN. Even if you want to use dynamic routing protocols to achieve inter-vlan routing, this process is often done via connected routes, with AD of 0, causing routing protocols to never be used in the first place.

Other types of routing like dynamic routing procols can be used when you want routers to dynamically select specific paths to forward data under specified conditions.