Details about the association between a layer-3 Switch and a vro

A layer-3 Switch uses a new technology that combines layer-3 routing and layer-2 switching. If a large network is divided into small local networks by department, region, and other factors, the layer-3 Switch plays a core role.

In recent years, with the rapid development of information technology in the Internet and enterprises, layer-3 switches and routers have increasingly become a sense that traditional routers have changed from the original traffic controllers to the current bottlenecks. Vswitches with layer-3 routing can replace or partially complete the functions of traditional routers on the layer-3 protocol, and have a speed of almost layer-2 switching.

And the price is relatively low. At that time, many people began to think of a layer-3 Switch to replace the router! But what is the truth? Traditional routers play the roles of isolated networks, isolated broadcast, route forwarding, and firewall in the network. With the continuous development of the network, their workload is also growing rapidly.

Nowadays, VLAN technology is widely used in networks for convenience of security and management. VLAN technology can logically isolate different network segments, ports, and even hosts. Communication between different VLANs must be forwarded through routers. Because of the large data traffic in the LAN, a large amount of information exchange between VLANs must be forwarded through routers. At this time, as the data traffic increases, routers become the bottleneck of the network.

Layer-3 switches use a new technology that combines layer-3 routing and layer-2 switching. Data is transmitted in segments in the network. layer-3 switching technology addresses and forwards the first data segment of a data stream, then, create a MAC ing table between the MAC address and IP address of the data stream in the cache.

When subsequent data streams arrive at the vswitch, The ing table is used to forward the data directly from the second layer to the destination exit, instead of using the layer-3 routing function. Because of this, layer-3 switching technology reduces the network latency caused by route addressing and forwarding, and improves the packet forwarding efficiency.

However, technically, there are significant differences between vrouters and vswitches in the packet exchange process. The router adopts the longest matching method, which is complicated to implement. It is completed through the microprocessor-based software. For layer-3 switching, its route forwarding is for a certain data stream, and the CACHE technology is used to store ing tables, therefore, it is easy to use hardware-based ASIC chips.

As a result, it is not difficult to see that vrouters are more powerful than layer-3 vswitches! Functions such as NAT, VPN, and ACL cannot be completely replaced. In practice, the interconnection of subnets in the same LAN and the routing between VLANs in the LAN can be replaced by a layer-3 switch.

However, in a cross-regional network environment, a vro becomes an indispensable device. At the same time, a network fully built on a vswitch may encounter problems such as collision, congestion, and communication confusion. If you use a vro to divide the network into multiple subnets and use the functions of the vro to effectively control security policies, you can avoid these problems.

In addition, the layer-3 switch does not support the complete routing protocol yet, while the router is capable of simultaneously processing multiple protocols. When a network is connected to different protocols, such as a combination of Ethernet and card rings, it is impossible to complete inter-network routing and data transmission by relying on a layer-3 switch. In addition, the vro also has layer-4 network management capabilities, such as ACL security control over data streams, which is not available for layer-3 switches.

According to the characteristics of the three-tier switch and the router, the three-tier switch is not equal to the router, and it is impossible to replace the router! In our actual purchase, we should select products that suit our needs based on the characteristics of our network and possible future development needs.

In any case, with the development of technology and product improvement, the ultimate benefit will be our consumers! The emergence of local area networks has already gone through more than thirty years. During the past thirty years of development, the core CSMA/CD technology was introduced from the first wireless technology ALOHA to the Fast Ethernet 802.3u) and the emergence of modern GE802.3z) 10GE Ethernet technology, constantly new.

This raises a problem. For a specific network, it is difficult to choose a good networking technology because of the diversity of available networking methods. For users, the high reliability, high performance, easy maintenance, and easy expansion of the network are ensured under the premise of reducing the cost, which is closely related to the networking technology used;

For device manufacturers, how to make more profits based on ensuring the realization of users' network functions and the advantages and disadvantages of using networking technology is also a means to increase profits. At present, the development of technology can be said that the first-layer interface and second-layer exchange technology for users have become increasingly mature, and their development status is satisfactory. Therefore, the focus of selection is not at this level.

However, as the core of the network, there is no substantial breakthrough in the router technology that acts as the interconnection between networks. Therefore, a new routing technology came into being-layer-3 switching technology, which is a routing technology because it works on the layer-3 network protocol, the two-layer switching speed is almost possible.

In the trade-offs of these technologies, the choice of layer-2 switching + Routing networking and layer-3 switching networking is a focus. Who is the best or inferior of layer-2 switches, layer-3 switches, and routers, what environments are they applicable?

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To answer this question, we should first start with the working principles of these three technologies. 1) layer-2 switching technology the layer-2 switching technology is relatively mature. The layer-2 switch is a data link layer device that can identify the MAC address information in the data packet and forward it according to the MAC address, the MAC addresses and corresponding ports are recorded in an internal address table.

The specific workflow is as follows:

1) when the switch receives a packet from a port, it first reads the source MAC address from the packet header, so that it knows the port on which the machine with the source MAC address is connected; 2) read the target MAC address in the header and find the corresponding port in the address table;

3) if the table contains a port corresponding to the destination MAC address, copy the data packet to the port. 4) if the corresponding port cannot be found in the table, broadcast the data packet to all ports, when the target machine responds to the source machine, the switch can learn which port the destination MAC address corresponds to. The next time data is transmitted, it no longer needs to broadcast all ports.