Application point of view: Analysis of layer-3 Exchange access solutions

The Application of layer-3 switching is still very extensive. Here we mainly analyze the comprehensive description of the layer-3 switching access solution. The layer-3 switching access solution helps reduce the networking cost for networks with large scale and many downstream nodes.

At present, more and more companies need to build their own enterprise networks to connect their headquarters with their branches or offices distributed in different cities and regions to improve the company's
Improve service efficiency and market competitiveness. However, the shortcomings of the traditional router networking mode gradually emerge. factors such as high router costs, poor scalability, and complicated maintenance management restrict the development and promotion of the network. However, the three-layer exchange access solution helps reduce the network cost for networks with large scale and many downstream nodes.

Vro prices are relatively expensive compared with vswitches, and low-end vrouters do not support the G.703 ITU Standard on the physical and electrical characteristics of various digital interfaces, including 64kbps and 2.048Mbps interfaces) you must use the G/V converter device. In branch nodes, high-end routers are generally not configured, and even low-end routers are several times more expensive than switches. Therefore, the layer-3 switching access solution is applicable to networks with larger scales and more downstream nodes, the more substantial the savings are.

High port density and high scalability

Because the number of interfaces in a vro is small, for example, the maximum E1 port density of a Cisco 7513 vro is only 168, and the price of a single port is high, if you use a vswitch, there is no limit on the number of ports, for example, the 6509 M port density of the Cisco Catalyst 10/100 switch can reach 336, and more ports can be supported through cascade for more access.

Strong data processing capabilities

Generally, the packet forwarding rate of A vro is several hundred kpps and the bus bandwidth is 2 Gbps. The packet forwarding rate of A vswitch can reach over mpps, And the backboard bandwidth can be up to 32 Gbps. It can be seen that the data processing capability of a layer-3 switch is much higher than that of a router.

Support for multiple protocols

Like a router, a layer-3 switch supports many network protocols such as IP, IPX, and DECnet, such as RIPRouting Information Protocol and routing Information Protocol), OSPFOpen Shortest-Path First, open Shortest Path Priority Protocol), access example tables, and so on, vswitches can be implemented, while vswitches have some unique functions that cannot be implemented by vrouters.

Support for redundant channels

When the redundant channel is the same digital channel, the switch has a unique function that combines two or more identical physical links into one logical link, accumulating bandwidth, as long as one of the links is good, to maintain connectivity. This function is defined as Trunk On 3Com devices and Channel on Cisco devices. Its principles are similar and are implemented at the physical link layer. When a redundant channel is a digital channel and a simulated channel coexist, a router must be used. To avoid dynamic Routing occupying the WAN bandwidth, HSRP (Hot Standby Routing Protocol) can be selected on the branch node based on different products, hot Backup Router Protocol) or VRRP (Virtual Routing Protocol, Virtual Router redundancy Protocol), the center can use RIP or OSPF Dynamic Routing Protocol in the LAN to exchange Routing information between the Router and the switch.

High performance and price

The performance and price of the vro and vswitch are incomparable. However, the cost of the single-port equipment of the vro is much higher than that of the vswitch. For example, each port of a vswitch is 10 m ~ 10 thousand M Adaptive, and even 155 m optical port can be configured, while a 2 m E1 port of the router is as high as RMB. If the M Port module is used, the price is as high as 10 million RMB, A vro with a certain number of E1 port access costs RMB 100,000, while a layer-3 medium-and low-end switch requires RMB 100,000, and a high-end core switch only requires RMB. In enterprises with limited economic strength, it is a good way to save costs by adopting a three-tier exchange access solution.

Case Analysis

Taking a company's information network as an example, it is a typical star structure that connects the branches of each city with the Headquarters as the center. In this star wide area network topology that is connected to many nodes through digital channels, if the traditional network connection mode is used, there will be two important factors restricting the technical solution, that is, the limited processing capability and high cost of the router equipment.

Each company and each city branch has a CISCO C3560E layer-3 switch, and the entire network adopts the OSPF routing protocol. The circuit bandwidth from the headquarters to the branch is a 4 m digital circuit. The telecommunications company first binds two E1 circuits into a 4 m circuit, and then converts them into Ethernet interfaces through the photoelectric converter to access the Ethernet port of the C3560E switch.