VLAN aggregation (VLAN Aggregation, also known as Super VLAN) refers to the use of multiple VLANs (called Sub-VLANs) to isolate the broadcast domain in a physical network and aggregate these Sub-VLANs into a logical VLAN (called Super-VLAN) VLAN), these Sub-VLANs use the same IP subnet and default gateway, thus achieving the purpose of saving IP address resources.
Why do you need VLAN aggregation? First of all, we need to understand the deficiencies faced by ordinary VLAN or VLANIF.
In ordinary switching networks, VLAN technology has been widely used for its flexible control and deployment of the broadcast domain. However, in a general L3 switch, one VLAN corresponds to one VLANIF interface is usually used to realize the intercommunication between broadcast domains. In these cases, IP addresses will be wasted. Because in a subnet corresponding to a VLAN, the subnet number, subnet directed broadcast address, and subnet default gateway address cannot be used as the host IP address in the VLAN, and the actual access hosts in the subnet may be less than the number of addresses , The extra IP address will be wasted because it can no longer be used by other VLANs.
In order to solve the above problems, VLAN aggregation has occurred. It introduces the concepts of Super-VLAN and Sub-VLAN, so that each Sub-VLAN corresponds to a broadcast domain, and associates multiple Sub-VLANs with a Super-VLAN. By assigning an IP subnet to Super-VLAN, all Sub-VLANs use Super-VLAN IP subnets and default gateways for Layer 3 communication.
In this way, multiple Sub-VLANs share a gateway address, saving the subnet number, subnet directed broadcast address, and subnet default gateway address. They can be flexibly divided within the corresponding subnets of Super-VLAN according to the number of needs of their respective hosts The address range ensures that each Sub-VLAN as an independent broadcast domain realizes broadcast isolation, saves IP address resources, and improves the flexibility of addressing.
What is Vlan aggregation and basic working principle? VLAN aggregation defines Super-VLAN and Sub-VLAN so that Sub-VLAN only contains physical interfaces and is responsible for keeping separate broadcast domains; Super-VLAN does not contain physical interfaces and is only used to establish Layer 3 VLANIF interfaces. Then, by establishing the mapping relationship between Super-VLAN and Sub-VLAN, the three-layer VLANIF interface and the physical interface are organically combined to realize that all Sub-VLANs share a gateway to communicate with the external network, and use ARP Proxy to realize Sub-VLAN Between the three layers of communication, so as to achieve the purpose of saving the IP address while realizing the isolated broadcast domain of the ordinary VLAN.
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