Main differences between layer-3 vswitches and vrouters

Layer-3 switches are quite common, So I studied the differences between layer-3 switches and vrouters. I would like to share with you here, hoping they will be useful to you. Before the emergence of layer-3 switching technology, there was almost no need to distinguish routing devices from routers. They were exactly the same: Providing routing functions is working on routers. However, currently, layer-3 vswitches can fully perform most of the functions of traditional routers. As a device for network interconnection, layer-3 switches have the following features:

1. forward business flows based on layer-3 addresses;
2. full exchange of functions;
3. Special services such as packet filtering or authentication can be completed;
4. perform or not perform route processing.

Layer-3 vswitches have the following advantages over traditional vrouters:

1. transmission bandwidth between subnets can be arbitrarily allocated: each interface of a traditional router connects to a subnet, and the transmission rate of the subnet through the router is limited by the bandwidth of the interface. The layer-3 switch is different. It can define multiple ports as a virtual network and use a virtual network composed of multiple ports as a virtual network interface, the information in the virtual network can be sent to the layer-3 Switch by forming a virtual network port. The number of ports can be specified arbitrarily, so there is no limit on the inter-subnet transmission bandwidth.

2. reasonable configuration of Information Resources: As there is no difference between the resource rate in the subnet access and the resource rate in the global network access, it is of little significance to set a separate server in the subnet. Setting a server group in the global network not only saves money, more reasonable configuration of information resources.

3. Cost Reduction: Generally, vswitches are used to form subnets and vrouters are used to interconnect subnets. Currently, layer-3 vswitches are used for network design. They can be divided into any virtual subnets, and can communicate between subnets through the layer-3 routing function of vswitches. This saves expensive vrouters.

4. Flexible Connections between vswitches: As vswitches, no loops are allowed between them. As vrouters, there are multiple channels to improve reliability and balance load. The layer-3 Switch uses the Spanning Tree Algorithm to block the loop port. However, when routing is selected, the blocked path is still used as the optional path for route selection.

Recently, I have seen many people asking what the vswitch and vro are, what are their functions, and what are their differences. I will give some simple answers to these questions. A switch, also known as an exchange hub, can be used to connect some machines to form a LAN. A vro differs significantly from a vswitch. Its function is to connect different network segments and find the most suitable path for data transmission in the network. In general, individual users have little need. A vro is generated after a vswitch, just as a vswitch is generated after a hub. Therefore, the vro and vswitch are also associated, and they are not completely independent of each other. Vro mainly overcomes the problem that vswitches cannot route and forward data packets. At present, I am personally using ADSL for many broadband access methods. Therefore, I will give a brief description of the access to ADSL. Most of the purchased ADSL cats have many routing functions. When the manufacturers leave the factory, the routing function is blocked, because most of them do not enable the routing function during Telecom installation and DHCP is enabled. Enable the ADSL routing function). If an individual accesses the Internet or a few computers pass through ADSL, you only need to purchase one or more hubs or switches if the computer is large.

Please purchase a vswitch because the price difference between the hub and the vswitch is very small. There is no need to pursue high prices, because product homogeneity is very serious today, and there is no problem with my cheapest switch. We recommend that you purchase an eight-port service to meet the expansion requirements. The general price is about 100 yuan. Connect all the computers to the vswitch. The only thing to do is to insert the network cable of each machine into the interface of the switch and insert the cat network cable into the uplink interface. Then you can set the routing function and DHCP to share the internet. After reading the above explanation, you should have some knowledge about vswitches and vrouters. The current usage is mainly based on the combination of vswitches and vrouters, the specific combination method can be determined based on the specific network conditions and requirements.

Differences between vswitches and vrouters

A computer network is often composed of many different types of network connections. If several computer networks are physically connected together and cannot communicate with each other, then this "interconnection" is meaningless. Therefore, when talking about "interconnection", it is suggested that these computers can communicate with each other. That is to say, in terms of functions and logic, these computer networks have formed a large computer network, or an interconnected network, or Internet. Some intermediate devices or systems are used to connect networks. ISO is called relay. Based on the level of the relay system, there can be the following five relay systems:

1. The physical layer is often referred to as the first layer and layer L1) repeater system ).
2. data link layer (Layer 2), that is, bridge or bridge ).
3. Layer 3, layer L3) relay system, that is, router ).
4. A mixture of bridges and routers. The bridge router has the functions of bridges and routers.
5. A relay system above the network layer, that is, the gateway ).

When the relay system is a forwarder, it is generally not called network interconnection, because it only expands a network, and it is still a network. High-level gateways are rarely used due to their complexity. Therefore, network interconnection generally refers to the network in which vswitches and vrouters are interconnected. This article describes the differences between vswitches and vrouters.

Vswitch and vro applications

"Exchange" is the most frequently used word on the network today. It can be applied on any occasions from the bridge to the ATM to the telephone system. It is hard to figure out what is the real exchange. In fact, the word exchange first appeared in the telephone system, specifically to achieve the exchange of voice signals between two different telephones, the device to complete this work is the telephone switch. Therefore, in terms of intention, exchange is only a technical concept, that is, to complete the forwarding of signals from the device entry to the exit. Therefore, any device that complies with this definition can be called an exchange device. It can be seen that "Exchange" is a widely used term. When it is used to describe the second layer of the data network, it actually refers to a bridge device; when it is used to describe the third-layer device of the data network, it also refers to a routing device. We often mention that an Ethernet switch is actually a multi-port L2 network device based on the bridge technology, it provides low-latency and Low-overhead channels for data frame forwarding from one port to another.

It can be seen that the core of the layer-3 switch should have an exchange matrix to provide a channel for communication between any two ports or a fast exchange bus, to send data frames received by any port from other ports. In actual devices, the function of the switching matrix is usually completed by a dedicated chip ASIC. In addition, there is an important assumption in the design philosophy of the Ethernet switch, that is, the speed of the switching core is very fast, so that the normal large-volume data will not cause congestion. In other words, the exchange capability is infinite relative to the information transmitted. In contrast, the design of the ATM switch is that the exchange capability is limited compared with the Information transmitted ). Although the second layer Ethernet switch is developed based on a multi-port bridge, after all, the switch has more features, making it the best way to get more bandwidth, it also makes the network easier to manage. A router is a packet exchange device or network layer relay device in the network layer of the OSI protocol model. The basic function of a router is to transmit data IP packets to the correct network, including:

1. IP datagram forwarding, including path finding and transmission of the datagram;
2. subnet isolation to prevent broadcast storms;
3. Maintain the route table and exchange route information with other routers. This is the basis for IP packet forwarding.
4. IP datagram error handling and simple congestion control;
5. Filtering and accounting of IP datagram.

Vrouters of different regions have different roles. On the backbone network, the main role of a router is routing selection. The router on the backbone network must know the path to all the lower-Layer Networks. This requires maintaining a large route table and responding to connection status changes as quickly as possible. A Router failure may cause serious information transmission problems. In the regional network, the main role of the router is network connection and route selection, that is, to connect to the lower-layer grass-roots network units-the campus network, while responsible for data forwarding between the lower-Layer Networks.

Inside the campus network, the main role of a router is to separate subnets. In the early days, the grass-roots unit of the Internet was LAN. All hosts were in the same logical network. With the continuous expansion of the network scale, the LAN has evolved into a campus network composed of multiple subnets connected to the high-speed trunk and router. The subnet is logically independent, and the router is the only device that can separate them. It is responsible for packet forwarding and broadcast isolation between subnets, the vro on the border is responsible for connecting to the upper-layer network.