The default setting of VLAN is that communication between VLANs is not allowed. To achieve communication between VLANs, a router must be used, but the router is a three-layer device, which not only involves hardware design but also software design, so the price is expensive, and The router must compare the destination address of each packet with its own routing table entry to determine the destination of the packet. The processing speed is very slow (relative to the speed of the LAN). A router should be used for VLAN in the core of a large network. The data exchange will greatly reduce the efficiency of the entire network, so people combine the rapid exchange capability of the switch with the routing addressability of the router, and the concept of three-layer exchange appears.
The third layer of switching works in the third layer of the OSI seven-layer network model, that is, the network layer. It uses the header information of the IP packets in the third layer protocol to mark subsequent data service flows. The packet is exchanged to the second data link layer, thereby opening a path between the source IP address and the destination IP address. This path passes through the second link layer. With this path, there is no need for the Layer 3 switch to unpack the received data packets every time to determine the route, but to directly forward the data packets and exchange the data streams. The connection between the Layer 3 switch and the Layer 2 switch is shown in the bottom figure. All data flows between VLANs are forwarded through the Layer 3 switch.
The biggest difference between Layer 3 switching and routing is that routing requires routing and forwarding of each data packet, while Layer 3 switching only performs route lookup for each communication's handshake connection and only Layer 2 forwarding of real user data, which is fast A lot. Since the layer 3 switch has routing capabilities, it also supports common routing protocols, such as static routing, RIP, OSPF, etc., and can be used as a pure multi-Ethernet port router. In addition, the software in the layer 3 switch is also very different from that in the router, except that some functions that are useful for the LAN, such as access control lists, are omitted, and many control functions are omitted, and the routing efficiency is greatly improved.
Part of Cisco's switch product introduction:
Cisco catalyst 2950 switches, Layer 2 switches, and Catalyst 2950 series include Catalyst 2950T-24, 2950-24, 2950-12, and 2950C-24 switches. Catalyst 2950-24 switch has 24 10/100 ports; 2950-12 has 12 10/100 ports; 2950T-24 has 24 10/100 ports and 2 fixed 10/100/1000 BaseT uplink ports; 2950C -24 has 24 10/100 ports and 2 fixed 100 BaseFX uplink ports. Catalyst 2950 has a 8.8Gbps switching backplane.
The Catalyst 3550 switch has a three-layer switching function and is divided into SMI and EMI. The former only supports static routing and RIP routing, and the latter supports routing protocols such as OSFP and EIGRP. Catalyst 3550 series include Cat3550-24 (24 * 10 / 100M + 2 * 1000M GBIC), Cat3550-48 (48 * 10 / 100M + 2 * 1000M GBIC), Cat3550-12T (10 * 1000M TX + 2 * 1000M GBIC) , Cat3550-12G (10 * 1000M GBIC + 2 * 1000M TX). Cat3550's backplane can reach up to 24Gbps.
The biggest difference between the Catalyst 3750 switch and the Catatlyst 3550 is that the 3750 supports Cisco StackWise stacking technology, which enables the stacking bandwidth of the Cat3750 to reach 16Gbps.
Catalyst 4500 series switches are upgraded products of the original 4000 series. They can be deployed at the core layer of small enterprises or the distribution layer of medium-sized enterprises. They support engine and power redundancy and provide online power supply. The Cisco Catalyst 4500 series includes three new Cisco Catalyst chassis: Cisco Catalyst 4507R (seven slots), Cisco Catalyst 4506 (six slots), and Cisco Catalyst 4503 (three slots). The switching performance of Cat4500 depends on its configured engine module, and the maximum can reach 64Gbps.
Catalyst 6000 switches can be deployed at the core layer of medium-sized enterprises. Cat6000 has super performance. With the help of Supervisor Engine 720 engine, it can achieve 720Gbps super backplane bandwidth.
The third layer of switching works in the third layer of the OSI seven-layer network model, that is, the network layer. It uses the header information of the IP packets in the third layer protocol to mark subsequent data service flows. The packet is exchanged to the second data link layer, thereby opening a path between the source IP address and the destination IP address. This path passes through the second link layer. With this path, there is no need for the Layer 3 switch to unpack the received data packets every time to determine the route, but to directly forward the data packets and exchange the data streams. The connection between the Layer 3 switch and the Layer 2 switch is shown in the bottom figure. All data flows between VLANs are forwarded through the Layer 3 switch.
The biggest difference between Layer 3 switching and routing is that routing requires routing and forwarding of each data packet, while Layer 3 switching only performs route lookup for each communication's handshake connection and only Layer 2 forwarding of real user data, which is fast A lot. Since the layer 3 switch has routing capabilities, it also supports common routing protocols, such as static routing, RIP, OSPF, etc., and can be used as a pure multi-Ethernet port router. In addition, the software in the layer 3 switch is also very different from that in the router, except that some functions that are useful for the LAN, such as access control lists, are omitted, and many control functions are omitted, and the routing efficiency is greatly improved.
Part of Cisco's switch product introduction:
Cisco catalyst 2950 switches, Layer 2 switches, and Catalyst 2950 series include Catalyst 2950T-24, 2950-24, 2950-12, and 2950C-24 switches. Catalyst 2950-24 switch has 24 10/100 ports; 2950-12 has 12 10/100 ports; 2950T-24 has 24 10/100 ports and 2 fixed 10/100/1000 BaseT uplink ports; 2950C -24 has 24 10/100 ports and 2 fixed 100 BaseFX uplink ports. Catalyst 2950 has a 8.8Gbps switching backplane.
The Catalyst 3550 switch has a three-layer switching function and is divided into SMI and EMI. The former only supports static routing and RIP routing, and the latter supports routing protocols such as OSFP and EIGRP. Catalyst 3550 series include Cat3550-24 (24 * 10 / 100M + 2 * 1000M GBIC), Cat3550-48 (48 * 10 / 100M + 2 * 1000M GBIC), Cat3550-12T (10 * 1000M TX + 2 * 1000M GBIC) , Cat3550-12G (10 * 1000M GBIC + 2 * 1000M TX). Cat3550's backplane can reach up to 24Gbps.
The biggest difference between the Catalyst 3750 switch and the Catatlyst 3550 is that the 3750 supports Cisco StackWise stacking technology, which enables the stacking bandwidth of the Cat3750 to reach 16Gbps.
Catalyst 4500 series switches are upgraded products of the original 4000 series. They can be deployed at the core layer of small enterprises or the distribution layer of medium-sized enterprises. They support engine and power redundancy and provide online power supply. The Cisco Catalyst 4500 series includes three new Cisco Catalyst chassis: Cisco Catalyst 4507R (seven slots), Cisco Catalyst 4506 (six slots), and Cisco Catalyst 4503 (three slots). The switching performance of Cat4500 depends on its configured engine module, and the maximum can reach 64Gbps.
Catalyst 6000 switches can be deployed at the core layer of medium-sized enterprises. Cat6000 has super performance. With the help of Supervisor Engine 720 engine, it can achieve 720Gbps super backplane bandwidth.
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