To configure a Layer 3 aggregation layer switch, create a Layer 3 link aggregation group, assign member interfaces, configure IP addresses, and set up routing for VLANs.

Step 1: Access Global Configuration

Enter the global configuration mode on your switch:

CodeCopyswitch> enableswitch# configure terminalswitch(config)#

This allows you to create aggregation interfaces and configure VLANs and IP addresses .

Step 2: Create a Layer 3 Aggregation Interface

Create a Layer 3 aggregate interface (LAG or EtherChannel):

CodeCopyinterface port-channel 1no switchportip address 10.10.10.1 255.255.255.0no shutdown

• no switchport ensures the interface operates at Layer 3.
• Assign an IP address to the aggregated interface for routing purposes .
• The port-channel number can range depending on your switch model (e.g., 1–256 on Aruba switches), .

Step 3: Add Member Interfaces

Add physical interfaces to the aggregation group:

CodeCopyinterface range GigabitEthernet1/0/1 - 2channel-group 1 mode activeno shutdown

• Use LACP (mode active) for dynamic aggregation or mode on for static aggregation.
• Ensure all member interfaces are Layer 3 capable and have the same speed and duplex settings .

Step 4: Configure VLANs and Subinterfaces (Optional)

If you need to route multiple VLANs over the aggregated link:

CodeCopyinterface port-channel 1.10encapsulation dot1Q 10ip address 10.10.10.1 255.255.255.0

• Each subinterface corresponds to a VLAN.
• Only traffic tagged with the VLAN ID will be processed by the subinterface .

Step 5: Configure Routing

Set up static or dynamic routing to enable Layer 3 connectivity:

CodeCopyip route 0.0.0.0 0.0.0.0 10.10.10.254

• For multiple VLANs, ensure each subnet has a corresponding interface or subinterface.
• Dynamic routing protocols (OSPF, EIGRP, BGP) can also be configured on the aggregated interfaces .

Step 6: Verify Configuration

Check the status of the aggregation interface:

CodeCopyshow etherchannel summaryshow ip interface briefshow running-config

• Ensure the port-channel is up and member interfaces are in the selected state.
• Verify IP addresses and routing are correctly applied .

Best Practices

• Ensure all member interfaces have identical speed, duplex, and VLAN configurations.
• Use LACP for automatic negotiation and redundancy.
• Monitor the operational key and aggregation state to detect misconfigurations.
• Document IP addressing and VLAN assignments for troubleshooting. By following these steps, you can configure a Layer 3 aggregation layer switch that provides high bandwidth, redundancy, and routing capabilities for your network .