L3 Switch
L3 switch is a switch with some router functions, and it works on the third layer of the OSI network standard model: the network layer. The most important purpose of L3 switch is to speed up the data exchange within a large LAN. The routing function it has there is to serve the speed purpose. It can be routed once and forwarded many times. L3 switch runs on the layer 3 “network” and layer 2 “data link”.
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Router
The router connects two or more network devices and acts as a gateway between the networks. It reads the address in each data packet and then decides how to transmit it. It is a dedicated intelligent network device. It can understand different protocols, such as the Ethernet protocol used by a local area network and the TCP/IP protocol used by the Internet. In this way, the router can analyze the destination addresses of data packets from various types of networks, and convert the addresses of non-TCP/IP networks into TCP/IP addresses, or vice versa; the best route is sent to the designated location. So, the router can connect non-TCP/IP networks to the Internet.
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Difference between a three-layer switch and a router
1. Regarding OSI layer: First of all, the router is a L3 device, working at the network layer. While the L3 switch can work at both L3 “network layer” and L2 “data link” layer at the same time.
2. The router and switch were integrated in the early days: As the core equipment of the early network, the router integrated the function of the switch, but due to the limited forwarding capability of the layer2, the early one-arm routing function was provided for the communication between VLANs, but as the core equipment of the network, it must have high-speed Forwarding capabilities, routers provide too few Ethernet interfaces. Therefore, the Layer 3 switch replaces the router at the core of the LAN.
3. The function of the three-layer switch is not as good as the router: Routers are professionally capable of processing Layer 3 messages (data packets), while L3 switching is not very professional to support L3 functions. It only provides simple routing functions and some Layer 3 filtering functions. The router is based on three layers, supports WAN connection, rich WAN interfaces, including serial, ATM, etc., supports a variety of different wired transmission media, including serial cables, optical fibers, telephone lines, dedicated lines, etc., and supports WAN connections on the interface The encapsulation type supports HDLC, FR, ATM, PPP, ISDL encapsulation, which are not available in Layer 3 switches. Layer 3 switches only contain a large number of Ethernet interfaces, they cannot completely replace routers.
4. Can Layer 3 switches replace routers? some people will say that since the L3 switch has the function of a router. L3 switch does the L2 work and L3 work, you will find that the efficiency is very low. In addition, the router can be said to be the first firewall of the intranet, and the security of the switch is still not enough to replace it. In addition, the very high-end Layer 3 switches can support the connection of the WAN, but need to add related business modules to achieve such a function.
