Difference between VLAN and subnet

VLAN vs subnet

What is a VLAN ??


VLAN is a logical group of networks created independently of their physical location, which allows the creation of smaller broadcast domains within a switch. For these VLANs, different ports can be assigned. Without a VLAN, a switch assumes that all interfaces on a switch are in a single broadcast domain. VLANs provide broadcast filtering, security address, summary, traffic flow management and reduce the workload for the Spanning Tree protocol by limiting a VLAN to a single access switch. This is useful when Layer 3 networks are to be created in a Layer 2 switch.

VLANs are a kind of tagged link between switches; they can be linked together, or a Layer 3 switch or router can interconnect them. VLANs have the same attributes as a LAN, but they assign devices regardless of their physical location. Each switch has a default VLAN of VLAN 1 enabled on the switch. Although a name for a VLAN is assigned, only the VLAN number is important when sending traffic. The VLAN ID, identical to the VLAN number, is added when a packet leaves a shared port. Devices in a VLAN group use the same VLAN ID. The most common VLAN protocols are dot1q and isl, and they are used for inter-VLAN communication. There are two methods for assigning a VLAN; they are called static VLAN and dynamic VLAN. Static VLANs are port-based and dynamic VLANs are created software help. The VLAN standard is IEEE 802.1 Q.

What is the subnet ??


The subnet or subnet is a subdivision of an IP network. Breaking a large network into several small networks is called a subnet. We group a network with a network mask to form a subnet mask. The subnet reduces network traffic, optimizes network performance, and simplifies management. The subnet increases the complexity of routing because, in a table, each subnet is represented by a separate entry. A router is required to connect these networks. In IPv4, the main reason for creating subnets is to improve efficiency and use a limited network address. The IPv4 network includes 256 IP addresses. If only 14 of these 256 IP addresses are assigned to a VLAN, the remaining 240 will become useless. To overcome this waste of IP addresses, we can divide this network into subnets, which includes 16 IP addresses. Then assign these addresses to the relevant group and assign other addresses to another group or save them for later use. A local area network, a member of a global internetwork, is normally called a subnet router. An address mask is used to define a sub-address limit, called a subnet mask for this particular local network.

What is the difference between VLAN and subnet?



  • VLANs allow you to isolate a smaller subnet on a single device. With a smaller subnet, you have fewer devices and this generates less broadcast traffic. But this increase in the volume of unicast traffic between networks, which makes the CPU usage high.
  • There is a one-to-one relationship between VLANs and subnets, which means that a subnet can be assigned to a VLAN. Although it is possible, trying to assign more than one subnet to a VLAN is not good planning for network design.
  • The VLAN limit marks the end of a logical subnet.
  • For MPLS, it is better to create more subnets than to create more VLANs, because MPLS creates shortcuts between IP subnets for fast performance.
  • VLANs are useful when we need to create IP subnets that spread over an area as large as the university, when connecting faculties or buildings.
  • Simply put, VLAN = a broadcast domain = IP subnet.

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