Part I. The Routing Connection of Layer 3 Ethernet Switch
The Layer 3 switch also supports routing to achieve the connection of different subnets. However, what should be noted is that its routing doesn’t perform as well as the router’s routing. Layer 3 switch’s routing can only be used for the same type of network interconnection and usually only for the interconnection between LAN subnets. It cannot connect a LAN with a WAN or the Internet because Layer 3 switch support very limited routing protocols. After all, routing isn’t its main function.
As we all know, on the LAN, the Layer 2 switch identifies the sender of the data packet through the source MAC address, and forwards the data packet according to the destination MAC address. For packets whose destination addresses are not on the LAN, the Layer 2 switch cannot send them directly to the destination. It needs to be forwarded through a routing device such as a traditional router. At this point, the switch must be connected to the routing device such as the traditional router. If the default gateway of the switch is set as the IP address of the routing device, the switch will send the data packets that need to be forwarded to the routing device through routing.
The routing device examines the destination address of the packet and its own routing table. If a forwarding path is found in the routing table, the routing device forwards the data packet to other network segments. Otherwise, the packet will be dropped. A dedicated router is expensive, complex, slow, and can easily become a network bottleneck because it needs to analyze all broadcast packets and forward some of them. It also needs to exchange routing information with other routers. These processes are handled by the CPU (rather than a dedicated ASIC).
The Layer 3 switch can not only identify and forward data packets by MAC address like a Layer 2 switch but also route and forward between two network segments like a traditional router. Traditional routers use software to maintain routing tables, while Layer 3 switch handle routing and forwarding through dedicated ASIC chips. Compared with traditional routers, the routing speed of the Layer 3 switch is usually ten or dozens of times faster.
The routing connection of the Layer 3 switch is shown in the figure below.
Part II. Related Product: V-SOL Layer 3 Ethernet Switch
V-SOL has different series of Ethernet switches with various ports and performances. Here we take an example with the V35XX series Layer 3 switch that includes V3528EF, V3528E, V3528-P, and V3552E.
These Layer 3 switches can be applied in different scenarios such as SOHO, public zone, enterprise, etc. Like the V3528-P PoE switch, it has PoE function to supply power for terminal devices such as AP or IPC in public areas. Moreover, the V3528EF switch mainly converges the data from other swithes or OLT that access the data.
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