Analysis of Cisco layer-3 Switch stack connection

Source: Internet
Author: User

The Cisco layer-3 switch is another core switch developed by Cisco. It aggregates the bandwidth of the backboard of the switch that is stacked together, in this way, the total backplane of the switch stack is the sum of the bandwidth of several stack switches.

Note that not only the ports used are different, but the cables used are different: the cascade ports must be used for common direct connections; the cascade cable using a common port is a crossover cable, just like a pair of two hosts.

As for the stack of a Cisco layer-3 Switch, not all switches can, but must have a stack module. The stack of A vswitch is connected through a dedicated stack cable instead of a switching port.

Note that because the switch stack is usually placed in the same position and the connection cable is short, the stack of the switch is mainly used to expand the switch port, rather than to expand the distance. In addition, the switch stack can increase the available bandwidth of each actually used switch port.

Because it aggregates the bandwidth of the vswitch together, the total bandwidth of the vswitch stack is the sum of the bandwidth of several stack switches. When the bandwidth of the backboard is increased, if each port of the switch is used.

This advantage is not very obvious but also effective, because it is impossible to communicate with each port at the same time), but if there is a vswitch port available, the effect will be more obvious, because it can make full use of all the bandwidth of the switch.

The stack connection port of the switch is usually in the D-Jack format. A switch has two such ports marked with "UP" and "DOWN", as shown in ), it indicates that it is used to connect up and up the stack, and cannot be connected to an error.

Route connection of a Cisco layer-3 Switch

As we mentioned earlier, layer-3 switches also have certain "routing" functions to achieve connections between different subnets. However, it should be noted that its routing function is much weaker than that of a router. The routing function of a layer-3 switch can only be used for network interconnection of the same type,

Generally, it is only the interconnection between LAN subnets that cannot connect the LAN to the WAN or the Internet, because the routing protocols supported by layer-3 switches are very limited. After all, this is not its main function. We know that on the LAN, a layer-2 switch identifies the packet sender through the source MAC address and forwards the packet according to the destination MAC address.

Send data packets. For a data packet whose destination address is not on the local area network, the Cisco layer-3 Switch cannot directly send it to the destination. It must be forwarded through a routing device such as a traditional router, connect the vswitch to the routing device.

  • Technical issues of L2 Switches
  • Analysis of LAN switch Classification
  • Analyze the differences between bridges and switches
  • Differences between traditional vswitches
  • Details about how a vswitch works

If you set the default gateway of A vswitch as the IP address of the router device, the Cisco L3 switch sends the packet to be forwarded by the route device. The routing device checks the destination address of the data packet and its route table. If the forwarding path is found in the routing table.

The routing device forwards the data packet to other network segments. Otherwise, the data packet is discarded. A dedicated router is expensive, complex, slow, and easy to become a network bottleneck because it needs to analyze all the broadcast packets and forward some of them, and exchange route information with other routers, and these processes are all handled by the CPU rather than the dedicated ASIC ).

A layer-3 switch can identify and forward data packets through a MAC address like a layer-2 switch, and can also forward data packets between two CIDR blocks as a traditional router. Traditional routers use software to maintain route tables, while layer-3 switches use dedicated ASIC chips to process route forwarding. Compared with traditional routers, the routing speed of layer-3 switches is generally 10 times faster or dozens of times faster.

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