Analysis of Cisco switch link aggregation instances

Link AggregationThere are port aggregation and port bundling. The English name is porttrunking. The function isVswitchTo achieve load balancing. Avoid link congestion. Through configuration, You can bind two or four ports to forward data on specific ports to prevent packet loss when the forwarding rate of a single link is too low.

Advantages of Trunking: The price is low, and the performance is close to that of Gigabit Ethernet. You do not need to reWiring or consider the limitations of the gigabit network transmission distance. trunking can bind any related ports, you can also cancel the settings at any time, which provides high flexibility and load balancing capabilities and system fault tolerance. The following describes two related commands:

1. command:

Port-group Mode {active | passive | on}

Noport-group

Function: adds a physical port to the PortChannel. The no operation of this command is to remove the port from the PortChannel.

Parameters: The Group Number of the PortChannel. The value range is 1 ~ 16; active0) The LACP protocol of the Start port, and set it to Active mode; passive1) The LACP protocol of the Start port, and set it to Passive mode; on2) force the port to join the PortChannel, do not start LACP.

For example, in port Ethernet0/0/1 mode, add this port to port-group in active mode.

SwitchConfig-Ethernet0/0/1) # port-group1modeactive

2. command:

Interfaceport-channel

Function: Enter the aggregation interface configuration mode.

Command mode: global configuration mode

Example: Entering port-channel1 Configuration Mode

Switch (Config) # interfaceport-channel1Switch (Config-If-Port-Channel1 )#

Example of link aggregation Application

If ports 1, 2, and 3 on Switch1 are both access ports and belong to vlan1, add the three ports as active ports to group1, and ports 6, 8, and 9 on Switch2 are trunk ports, and it is allowall. Add the three ports to group2 in passive mode and connect the corresponding ports to the network cable respectively.

Link aggregation method 1:

The steps for configuring link aggregation are as follows:

 
 

  
  
Switch1#config  
  
  
 
  
  
Switch1(Config)#interfaceeth0/0/1-3  
  
  
 
  
  
Switch1(Config-Port-Range)#port-group1modeactive  
  
  
 
  
  
Switch1(Config-Port-Range)#exit  
  
  
 
  
  
Switch1(Config)#interfaceport-channel1  
  
  
 
  
  
Switch1(Config-If-Port-Channel1)# 
 
 

 
 

  
  
Switch2#config  
  
  
 
  
  
Switch2(Config)#port-group2  
  
  
 
  
  
Switch2(Config)#interfaceeth0/0/6  
  
  
 
  
  
Switch2(Config-Ethernet0/0/6)#port-group2modepassive  
  
  
 
  
  
Switch2(Config-Ethernet0/0/6)#exit  
  
  
 
  
  
Switch2(Config)#interfaceeth0/0/8-9  
  
  
 
  
  
Switch2(Config-Port-Range)#port-group2modepassive  
  
  
 
  
  
Switch2(Config-Port-Range)#exit  
  
  
 
  
  
Switch2(Config)#interfaceport-channel2  
  
  
 
  
  
Switch2(Config-If-Port-Channel2)#  
 
 

Link aggregation configuration result:

After a period of time, shell prompts that the port aggregation is successful, at this time Switch1 Port 1, 2, 3 converge into a aggregation port, the aggregation port name is Port-Channel1, Switch2 port 6, 8, 9 converge into a aggregation port, the aggregation port is named Port-Channel2, and can enter the aggregation interface configuration mode for configuration.

Link aggregation method 2: Configure PortChannel in the on mode.

The steps for configuring link aggregation are as follows:

 
 

  
  
Switch1#config  
  
  
 
  
  
Switch1(Config)#interfaceeth0/0/1  
  
  
 
  
  
Switch1(Config-Ethernet0/0/1)#port-group1modeon  
  
  
 
  
  
Switch1(Config-Ethernet0/0/1)#exit  
  
  
 
  
  
Switch1(Config)#interfaceeth0/0/2  
  
  
 
  
  
Switch1(Config-Ethernet0/0/2)#port-group1modeon  
  
  
 
  
  
Switch1(Config-Ethernet0/0/2)#exit  
  
  
 
  
  
Switch1(Config)#interfaceeth0/0/3  
  
  
 
  
  
Switch1(Config-Ethernet0/0/3)#port-group1modeon  
  
  
 
  
  
Switch1(Config-Ethernet0/0/3)#exit 
 
 

 
 

  
  
Switch2#config  
  
  
 
  
  
Switch2(Config)#port-group2  
  
  
 
  
  
Switch2(Config)#interfaceeth0/0/6  
  
  
 
  
  
Switch2(Config-Ethernet0/0/6)#port-group2modeon  
  
  
 
  
  
Switch2(Config-Ethernet0/0/6)#exit  
  
  
 
  
  
Switch2(Config)#interfaceeth0/0/8-9  
  
  
 
  
  
Switch2(Config-Port-Range)#port-group2modeon  
  
  
 
  
  
Switch2(Config-Port-Range)#exit 
 
 

Link aggregation configuration result:

After adding the Ports 1, 2, and 3 on Switch1 to the port-group1 in sequence, we can see that it is mandatory to join a group in the on mode, the switches at both ends will not achieve convergence by switching LACPPDU, convergence is also triggered, when the knock into the port 2 to add the port-group1 command, 1 and 2 together to form a port-channel1, when Port 3 is added to the port-group1, The port-channel1 1 and 2 are split up, and the three ports 1, 2, and 3 are re-converged into the port-channel1, to add a new port to a group that has been successfully merged, you must first split the original group and then aggregate it into a new group ). The result is that the three ports ON Switch1 2 and Switch1 2 are all aggregated in the ON mode, forming an aggregation port respectively.

Link aggregation summary:

1: Spanning Tree and STP are mainly used to avoid loops and redundant networks. Multiple links are often used to generate loops, broadcast storms, and network paralysis, note that do not forget the startup of the spanning tree when the network is involved. 3. For example, in a large enterprise, the core switch and other switches are connected by two network cables. In this case, one of the switches may have an error and the other switch can work. However, if PC2 and PC1 communicate with each other, loops may occur, generate broadcast storms. The spanning tree can solve this problem.

2: link aggregation: the main function of link aggregation is to increase the network bandwidth. One is to connect two vswitches, for example, two vswitch devices, with one 10-Gigabit network cable cascade, because the two access ports are too large, blocking will occur and the speed will be slow. At this time, you can use link aggregation, use the port-group command to create link aggregation, and use two network cables to connect to the switch, the ports connected to the two vswitches are aggregated to increase the network bandwidth.

Another scenario of link aggregation is that a switch is linked between servers. For example, if a server is connected to a switch, the server will not be able to withstand the high traffic volume, you can use link aggregation to aggregate the ports connected to the two NICs to relieve the server load.