EtherChannel (LACP) - CSU359 - Shoolini University

Configure and verify (Layer 2/Layer 3) EtherChannel (LACP)

0. Layer 2

Layer 2 of the OSI model, known as the Data Link Layer, is responsible for node-to-node data transfer. It ensures data is formatted correctly and handled securely when it moves between devices on the same network segment. Layer 2 handles hardware addressing through MAC addresses and provides methods for error detection and correction.

0.1 Key Functions of Layer 2

Layer 2 performs several important functions in a network:

0.2 Layer 2 Devices

The most common devices operating at Layer 2 are switches and bridges:

0.3 Layer 2 Frame Structure

A typical Layer 2 Ethernet frame consists of the following fields:

1. Layer 3

Layer 3 of the OSI model, known as the Network Layer, is responsible for logical addressing and routing. It determines how data is transmitted between devices across different networks, ensuring that packets are delivered to their correct destination. Layer 3 uses IP addresses to handle packet forwarding and provides essential functions like routing, fragmentation, and traffic control.

1.1 Key Functions of Layer 3

Layer 3 performs several vital tasks in network communication:

1.2 Layer 3 Devices

The primary devices that operate at Layer 3 are routers and Layer 3 switches:

1.3 Layer 3 Packet Structure

A typical Layer 3 IP packet consists of the following fields:

2. EtherChannel and LACP

EtherChannel is a technology used to combine multiple physical links into a single logical link to increase bandwidth, provide redundancy, and improve network reliability. It allows multiple Ethernet links to act as one logical link between devices like switches, routers, and servers. This ensures load balancing and fault tolerance. EtherChannel can operate at both Layer 2 and Layer 3 of the OSI model.

LACP (Link Aggregation Control Protocol) is an open standard protocol (IEEE 802.3ad) used to manage the dynamic formation of EtherChannels. It allows switches to automatically form an EtherChannel by negotiating with the connected devices, determining which links can be bundled together.

2.1 Benefits of EtherChannel

2.2 Modes of EtherChannel

EtherChannel can operate in different modes depending on whether it uses LACP, PAgP (Cisco proprietary protocol), or no protocol (static configuration):

2.3 LACP Configuration Example


Switch(config)# interface range gigabitEthernet 1/0/1 - 2
Switch(config-if-range)# channel-group 1 mode active
Switch(config-if-range)# exit
Switch(config)# interface port-channel 1
Switch(config-if)# switchport mode trunk

Explanation: This configuration creates an EtherChannel group (channel-group 1) using LACP in active mode. The port-channel is configured as a trunk to allow VLAN traffic.

2.4 Verifying EtherChannel with LACP

Verification commands help ensure that the EtherChannel is functioning correctly and efficiently:


Switch# show etherchannel summary
Switch# show interfaces port-channel
Switch# show lacp neighbor

Explanation:

3. Configure and Verify (Layer 2/Layer 3) EtherChannel (LACP)

EtherChannel is a technique used to bundle multiple physical links into one logical link to increase bandwidth and provide redundancy. This can be configured in both Layer 2 (switching) and Layer 3 (routing) environments. LACP (Link Aggregation Control Protocol) is an open standard protocol used to dynamically form and manage EtherChannels.

3.1 Layer 2 EtherChannel Configuration (Switching)

In a Layer 2 environment, EtherChannel aggregates multiple switch ports to act as one logical port. This improves bandwidth and ensures redundancy in case one of the physical links fails.

The configuration steps for Layer 2 EtherChannel using LACP:

3.1.1 Layer 2 EtherChannel Configuration Example

Switch(config)# interface range gigabitEthernet 1/0/1 - 2
Switch(config-if-range)# channel-group 1 mode active
Switch(config-if-range)# exit
Switch(config)# interface port-channel 1
Switch(config-if)# switchport mode trunk

Explanation:

3.2 Layer 3 EtherChannel Configuration (Routing)

In a Layer 3 environment, EtherChannel aggregates multiple routed interfaces, allowing logical bundling of interfaces for routing purposes.

Configuration steps for Layer 3 EtherChannel using LACP:

3.2.1 Layer 3 EtherChannel Configuration Example

Switch(config)# interface range gigabitEthernet 1/0/1 - 2
Switch(config-if-range)# channel-group 2 mode active
Switch(config-if-range)# exit
Switch(config)# interface port-channel 2
Switch(config-if)# no switchport
Switch(config-if)# ip address 192.168.1.1 255.255.255.0

Explanation:

3.3 Verifying EtherChannel (LACP)

Verification is crucial to ensure that EtherChannel is functioning as expected. The following commands help in verifying the configuration:


Switch# show etherchannel summary
Switch# show interfaces port-channel
Switch# show lacp neighbor

Explanation: