Layer-3 switch is not equal to vro

In recent years, with the rapid development of Internet/Intranet and the wide application of the B/S computing model, the cross-region and cross-network business has experienced a sharp increase. The industry and users are deeply aware of the bottleneck effect of traditional routers in the network. A layer-3 switch can operate on the layer-3 of the network protocol and act as a route. It has a speed that almost achieves layer-2 switching, and the price is relatively low. At that time, layer-3 switches will replace routers as the most popular topic in the network field. But is that true?

Traditional routers have routing forwarding, firewall, and broadcast isolation functions in the network. In a network with VLAN division, logically, the communication between different network segments still needs to be forwarded through the router.

Because the data volume of communication between different VLANs is large on the LAN, if the router needs to route each packet once, it will become a bottleneck as the data volume on the network increases. The third-layer exchange technology combines the routing and switching technologies.

After routing the first data stream, it will generate a ing table between the MAC address and IP address. When the same data stream passes through again, the table is directly routed from the second layer instead of the second layer, which eliminates the network delay caused by router selection and improves the efficiency of packet forwarding.

Router forwarding adopts the longest matching method, which is complicated and usually implemented by software. Layer-3 Switch routing lookup is targeted at the stream. It uses the CACHE technology and is easy to implement using ASIC. Therefore, it can greatly save costs and achieve fast forwarding.

However, technically speaking, there are significant differences between a router and a layer-3 Switch in Packet Exchange operations. Generally, a vro performs Packet Exchange Based on a microprocessor, while a layer-3 Switch performs Packet Exchange through hardware. Therefore, compared with a layer-3 Switch, vro features are more powerful, and functions such as NAT and VPN cannot be completely replaced.

The interconnection of subnets in the same LAN can be replaced by a layer-3 switch, but the lan must be interconnected with the public network to achieve a cross-regional network, then the router is indispensable. A network fully built on a vswitch may have problems such as collision, congestion, and communication confusion. Vrouters are used to divide networks into multiple subnets. You can avoid these problems by effectively implementing security control policies based on the functions of routes.

A layer-3 Switch cannot provide a complete routing protocol, while a router can process multiple protocols at the same time. When a network is connected to different protocols, such as a combination of Ethernet and card rings, it is impossible to transmit data between networks by using a layer-3 switch. In addition, vrouters also have layer-4 network management capabilities, which are not available in layer-3 vswitches.

Therefore, a layer-3 switch is not equal to a vro and cannot completely replace the vro.