Advantages of layer-3 vswitches

Compared with the original vswitch and vro, the routing speed of the layer-3 vswitch is generally 10 times faster or dozens of times faster, and can implement line rate routing forwarding and other functions, the exchange LAN technology enables dedicated bandwidth to be exclusive to users, greatly improving the efficiency of LAN transmission.

The introduction of LAN switches enables dedicated bandwidth between network sites, eliminating unnecessary Collision Detection and error re-transmission, and improving transmission efficiency, several independent communication processes can be maintained in parallel in the vswitch. In the exchange network environment, user information is transmitted only between the source node and the target node, and other nodes are invisible.

However, when a node sends a broadcast or multicast packet online, or a node sends a MAC address packet that the switch does not know, all nodes on the vswitch will receive this broadcast message. The entire exchange environment constitutes a large broadcast domain. Point-to-point is a fast and effective exchange on the second layer. However, broadcast storms can compromise network efficiency.

Layer-3 switches are much faster and cheaper than routers. It can be said that in the network system integration technology, the first-layer interface and the second-layer exchange technology that are directly oriented to users have obtained satisfactory answers. The exchange LAN technology enables dedicated bandwidth to be exclusive to users, greatly improving the efficiency of LAN transmission.

However, layer-2 switching also exposes vulnerabilities that cannot be effectively solved by broadcast storms, inter-network interconnection, and security control. As the core of the network, the router technology that acts as the interconnection between networks has no qualitative breakthrough. Most of today's enterprise networks have become the Intranets of Web technologies that implement TCP/IP protocols. User data is often transmitted across the local network over the Internet, so routers are often overwhelmed.

Traditional routers are software-based and have complex protocols. Compared with lan speed, their data transmission efficiency is low. At the same time, it serves as the hub for interconnection between network segments (subnets and VLANs), which makes traditional router technologies face severe challenges. With the rapid development of Internet/Intranet and the wide application of the B/S (Browser/Server) computing mode, cross-region and cross-network services have increased dramatically.

The industry and users are deeply aware of the bottleneck effect of traditional routers in the network. It is imperative to improve the traditional routing technology. One way is to install a super router with higher performance. However, this is too costly. If it is to build an exchange network, this investment is obviously unreasonable.

In this case, a new routing technology came into being. This is the layer-3 switching technology, also known as IP exchange technology and high-speed routing technology. The third layer exchange technology is proposed in contrast to the traditional exchange concept.

As we all know, the traditional exchange technology operates on the Layer 2-data link layer in the OSI Standard network model, the layer-3 switching technology implements high-speed packet forwarding in the network model. Simply put, layer-3 exchange technology is layer-2 exchange technology + layer-3 forwarding technology.

This is a mechanism that uses information in the layer-3 protocol to enhance the functions of layer-3 switches. A device with layer-3 switching is a layer-2 switch with layer-3 routing, but it is an organic combination of the two, it is not simply to overlay the hardware and software of the router device on the LAN switch.

From the hardware implementation point of view, at present, the interface modules of the second layer switch exchange data through the High-Speed Backplane/bus (the speed can reach dozens of Gbit/s, in layer-3 vswitches, layer-3 router-related Routing hardware modules are also inserted on the high-speed backplane/bus.

In this way, the routing module can exchange data with other modules to be routed at a high speed, this breaks through the speed limit of the traditional external router interface (10 Mbit/s --- 100 Mbit/s ). In terms of software, layer-3 switches also have major initiatives. They define traditional software-based router software. The practice is:

1. For data packet forwarding, such as IP/IPX packet forwarding, these regular processes are implemented through hardware at high speed.

2. For layer-3 routing software, such as route information update, route table maintenance, route calculation, and route determination, Use optimized and efficient software. Assume that two sites using the IP protocol communicate with each other through the layer-3 Switch. When sending Site A, the IP address of the destination site is known, however, you do not know the MAC address required to send messages on the LAN.

IP Address Resolution (ARP) is used to determine the MAC address of the target site. The sending station compares its IP address with the IP address of the destination station, and extracts the network address using the subnet mask configured in the software to determine whether the destination station is in the same subnet as itself.

If the destination site B and the sender Station A are in the same subnet, A broadcasts an ARP request, and B returns its MAC address, after obtaining the MAC address of the target site B, A caches the address and uses the MAC address to package and forward data. The second layer switch module looks for the MAC address table to determine whether to send data packets to the target port.

If two sites are not in the same subnet, if Station A needs to communicate with Station C, station A must send an ARP (Address Resolution) packet to the "Default Gateway, the IP address of the "Default Gateway" has been set in the system software. This IP address actually corresponds to the layer-3 Switch module of the layer-3 switch.

Therefore, when the sender station A broadcasted an ARP request to the IP address of the "Default Gateway", if the layer-3 switching module obtains the MAC address of the destination station B in the previous communication process, then, send A reply to the MAC address of B. Otherwise, the layer-3 Switch module broadcasts an ARP request to the target site based on the route information.

After receiving the ARP request, the target Station C replies to the MAC address of the layer-3 Switch module. The layer-3 Switch module saves the address and replies to the sending station. Later, when packet forwarding between A and C is performed, the MAC address packet of the destination site will be used, and the data forwarding process will be handed over to the second layer for exchange, so that information can be exchanged at A high speed.

Compared with traditional routers, the routing speed of layer-3 switches is generally 10 times faster or dozens of times faster, enabling line rate routing forwarding. Traditional routers use software to maintain the route table, while layer-3 switches use ASIC Application Specific Integrated Circuit) hardware to maintain the route table, so as to achieve line-rate routing.

1. Correct Interpretation and test of vswitch Port
2. Summarize the market status of high-end Switches
3. Resolve core layer switch faults
4. PythonAndroid: Learn how to select a 24-port Gigabit Switch
5. Let's talk about the stacking of Ethernet switches.