For the first time in CSDN, published articles, please forgive me a lot!

This want to CSDN said some of the techniques, mainly discuss, with roommates last night

Let's talk about router and layer 3 switches some difference:

Although say is can support three layers, that why don't three layer layer 3 switches and also use the router? Why router still exist in the market? It must have its truth, but most of the time, in the face of others to put forward the difference between the layer 3 switches and routers, how do we reply?

First of all, we have to understand some of the concepts, the ARP table, RIB (routing table) and FIB (published) quickly,

1, design, they are composed of CPU and exchange chip, the CPU is mainly used to calculate the scene, such as computing routing overhead, OSPF the SPF algorithm, thus calculated by CPU routing table, according to the routing table to produce FIB table, a message after the first time will forward the CPU calculation according to the routing table, but its subsequent message will be forward by FIB list item, thus reducing The Times for the route table lookup to routers and layer 3 switches are also have a FIB, but layer 3 switches is primarily a FIB list items, mainly on the second floor of the FIB forwarding, layer 3 switches are mainly used at this moment is the exchange of it rather than the CPU chip, the router is forward three-tier FIB, because layer 3 switches or ARP message, the message on the second floor, and the router is not specifically for message on the second floor, mainly dealing with different network segment message,

2, the control ability, in general the router's control ability stronger than layer 3 switches, why do you say that??? Because general layer 3 switches is need through the VLAN control of different network segment, the router is directly through the interface to the control of different network segment, the router control on this level is more direct than layer 3 switches, one is the router on the control software can be controlled, such as QOS, many routers at the time of design, design resources stack, queue hundreds, and layer 3 switches is usually a few, and layer 3 switches is controlled by hardware, control the diversity of layer 3 switches as router,

3, the price is generally a router, prices are more expensive than the price of the switch on, it is just because of the routers in the network layer design than the layer 3 switching is reasonable, the design on the network layer to the transport layer is also more reasonable than layer 3 switches, such as policy routing, routing policy, such as QOS,


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