How to Configure LACP Etherchannel on Cisco Switch in Packet Tracer

Link Aggregation Control Protocol (LACP) is the industry-standard protocol, defined by IEEE 802.3ad/802.1AX. It joins multiple physical interfaces connecting two switches or routers into a unified logical interface. This not only increase the overall bandwidth  but also establishes a redundant connection between the network devices.

etherchannel

In this post, I will show you how to Configure LACP Etherchannel on Cisco Switch in packet tracer

Key Features of LACP:

  • Bandwidth Enhancement: LACP allows for the aggregation of multiple physical interfaces, contributing to increased overall bandwidth.
  • Redundancy: The logical interface formed by LACP provides a redundant connection, ensuring network stability and fault tolerance.
  • Interface Scalability: LACP supports the aggregation of up to 8 active physical interfaces into one logical interface. Additionally, it allows for eight backup (failover) physical interfaces that can become active in the event of the failure of the currently active interfaces.
  • Port Compatibility: EtherChannels, including those formed with LACP, can be created using Ethernet ports, Fast Ethernet ports, Gigabit Ethernet ports, or even 10 Gigabit Ethernet ports.

Two Modes LACP:

LACP operates in two modes:

  1. Active Mode: In this mode, a switch actively initiates LACP negotiation by sending LACP packets to the neighboring switch. If the neighbor switch is also in active mode or passive mode and both devices have compatible parameters, an EtherChannel is formed.
  2. Passive Mode: In passive mode, a switch responds to LACP packets but does not actively send them. If the other switch is in active mode, the passive switch can form an EtherChannel with it if other parameters match.
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Network Topology

The network topology What we will be making use of in this post is as shown below. As you can see, it comprises two layer 2 switches and three physical interfaces connecting them. Because of the spanning tree protocol, which is enabled by default on Cisco switches, two ports on switch1 is  in a blocking state as indicated by the link light. This helps to avoid broadcast storms forming in the network.

In this demonstration, we will join the three physical interfaces into logical interfaces by configuring LACP on each of the layer 2 switches.

network topology for lacp configuration

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How to Configure LACP Etherchannel on Cisco Switch

Here are steps to Configure LACP Etherchannel on Cisco Switch

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Step 1: Create the portchannel

Enter the following commands to create portchannel on each of the switch

Switch0

SW0>enable
SW0#configure terminal
SW0(config)#interface range fa0/1-3
SW0(config-if-range)#channel-group 2 mode active

The command above creates a port channel of mode “active” using the fa0/1, fa0/2, and fa0/3 interfaces of switch0. As this channel is in active mode, it can form an etherchannel with switch1 even when switch1 is in passive mode.

Switch1

SW1>enable
SW1#configure terminal 
SW1(config)#interface range fa0/1-3
SW1(config-if-range)#channel-group 2 mode passive

Step 2: Verify Etherchannel Configuration

To verify the etherchannel configuration, enter the following command on each of the layer 2 switches to check if the etherchannel has been created. It can also be noticed that the ports in switch 1 have turned to a forwarding state (all link light has been turned to blue).

Switch#show etherchannel summary

etherchannel configuration

Switch1

SW1#show etherchannel summary
Flags:  D - down        P - in port-channel
        I - stand-alone s - suspended
        H - Hot-standby (LACP only)
        R - Layer3      S - Layer2
        U - in use      f - failed to allocate aggregator
        u - unsuitable for bundling
        w - waiting to be aggregated
        d - default port


Number of channel-groups in use: 1
Number of aggregators:           1

Group  Port-channel  Protocol    Ports
------+-------------+-----------+----------------------------------------------

2      Po2(SU)           LACP   Fa0/1(P) Fa0/2(P) Fa0/3(P) 

The flag (SU) means layer 2 etherchannel has been created and is in use.

Switch0

SW0#show etherchannel summary
Flags:  D - down        P - in port-channel
        I - stand-alone s - suspended
        H - Hot-standby (LACP only)
        R - Layer3      S - Layer2
        U - in use      f - failed to allocate aggregator
        u - unsuitable for bundling
        w - waiting to be aggregated
        d - default port


Number of channel-groups in use: 1
Number of aggregators:           1

Group  Port-channel  Protocol    Ports
------+-------------+-----------+----------------------------------------------

2      Po2(SU)           LACP   Fa0/1(P) Fa0/2(P) Fa0/3(P) 

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