Earlier in this module, you bundled multiple switch ports into one logical link with Layer 2 EtherChannel.
Now we move on to Layer 3 EtherChannel. The idea is the same: combine several physical interfaces into one Port-Channel. The difference is that the Port-Channel is treated as a routed interface and can be assigned an IP address instead of functioning as a switchport.
Figure 1 – Two switches linked before Layer 3 EtherChannel.
This type of configuration is supported on multilayer switches and routers. In Cisco's three-tier design (Access → Distribution → Core), it is commonly used between the Distribution and Core layers to ensure reliable, high-bandwidth interconnections.
In this lab, two multilayer switches (SW1 and SW2) will bundle interfaces F0/1 and F0/2 into Port-Channel 1.
Figure 2 – Port-Channel Setup
Each Port-Channel interface will then be assigned an IP address from the 192.168.1.0/24 network (a /24 network uses the mask 255.255.255.0; subnetting is covered later in this path).
Let's dive into the configuration.
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Configuration on SW1
Step 1 - Enable IP Routing
Since we are working with multilayer switches, we must first enable the global routing function.
By default, switches operate only at Layer 2. Theip routingcommand allows the switch to forward packets based on IP addresses.SW1# configure terminal Enter configuration commands, one per line. End with CNTL/Z. SW1(config)# ip routingAt this point, SW1 is ready to handle Layer 3 interfaces.
Step 2 – Convert Interfaces to Routed Ports and Create the EtherChannel (SW1)
Select the physical interfaces that will participate in the Layer 3 EtherChannel.
SW1(config)# interface range f0/1-2Convert the interfaces from Layer 2 switchports to Layer 3 routed ports.
SW1(config-if-range)# no switchportCreate a static EtherChannel using mode on.
SW1(config-if-range)# channel-group 1 mode on Creating a port-channel interface Port-channel 1 %LINK-5-CHANGED: Interface Port-channel1, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel1, changed state to up SW1(config-if-range)# exitThe system automatically creates the logical interface Port-Channel 1.
Step 3 – Assign an IP Address to the Port-Channel (SW1)
Configure the logical Port-Channel interface as a routed interface by assigning an IP address.
SW1(config)# interface port-channel 1 SW1(config-if)# ip address 192.168.1.1 255.255.255.0 SW1(config-if)# no shutdownConfiguration on SW2
Now, we apply the same Layer 3 EtherChannel principle on SW2.
The physical interfaces are converted to routed ports, bundled into a static EtherChannel, and an IP address is assigned to the logical Port-Channel interface.SW2# configure terminal Enter configuration commands, one per line. End with CNTL/Z. SW2(config)# ip routing SW2(config)# interface range f0/1-2 SW2(config-if-range)# no switchport SW2(config-if-range)# channel-group 1 mode on Creating a port-channel interface Port-channel 1 %LINK-5-CHANGED: Interface Port-channel1, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel1, changed state to up SW2(config-if-range)# exit SW2(config)# interface port-channel 1 SW2(config-if)# ip address 192.168.1.2 255.255.255.0 SW2(config-if)# no shutdownResult
At this stage, both switches are connected through a Layer 3 EtherChannel.
The logical Port-Channel 1 carries the IP configuration, while the physical interfaces F0/1 and F0/2 operate in parallel, providing redundancy and increased bandwidth.Answer the question below
Which command converts an interface to a routed port?
After completing the configuration, it is important to confirm that the Layer 3 EtherChannel is active and functioning correctly.
Check EtherChannel Summary
Use the
show etherchannel summarycommand to get an overview of the EtherChannel: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 ------+-------------+-----------+---------------------------------------------- 1 Po1(RU) - Fa0/1(P) Fa0/2(P)Explanation
RU → The Port-Channel is Routed (R) and Up (U).
P → Interfaces F0/1 and F0/2 are successfully bundled in the EtherChannel.
This confirms that the EtherChannel on SW1 is working properly.
The same check on SW2 gives an identical result:
SW2# 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 ------+-------------+-----------+---------------------------------------------- 1 Po1(RU) - Fa0/1(P) Fa0/2(P)Both outputs confirm that Port-Channel 1 is operational and the two interfaces are correctly aggregated.
Check IP Interfaces
Now let's verify the IP configuration with
show ip interface brief.SW1# show ip int brief Interface IP-Address OK? Method Status Protocol Port-channel1 192.168.1.1 YES manual up up FastEthernet0/1 unassigned YES unset up up FastEthernet0/2 unassigned YES unset up up SW2# show ip int brief Interface IP-Address OK? Method Status Protocol Port-channel1 192.168.1.2 YES manual up up FastEthernet0/1 unassigned YES unset up up FastEthernet0/2 unassigned YES unset up upBoth Port-Channel interfaces are up with the correct IP addresses, while the physical interfaces are unassigned (as expected).
Ping Test
Since we want to confirm that the Layer 3 EtherChannel is working as expected, we perform a connectivity test using a ping.
Figure 3 – Ping test across the Layer 3 EtherChannel.
We send a ping from SW1 to the IP address of the Layer 3 EtherChannel interface on SW2 (192.168.1.2):
SW1# ping 192.168.1.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.1.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 0/0/0 msThe ping is successful, confirming that the Layer 3 EtherChannel is up and operational.
Answer the question below
In the show etherchannel summary output, what letters confirm that the Port-Channel is Routed and Up?
Layer 3 EtherChannel combines multiple physical interfaces into a single logical routed interface.
Unlike Layer 2 EtherChannel, which works as a switchport, the Layer 3 Port-Channel is assigned an IP address and can participate in routing.Configuration Summary
Step 1 – Enable IP Routing SW1(config)# ip routing SW2(config)# ip routing Step 2 – Convert Interfaces & Create Port-Channel SW1(config)# interface range f0/1-2 SW1(config-if-range)# no switchport SW1(config-if-range)# channel-group 1 mode on SW2(config)# interface range f0/1-2 SW2(config-if-range)# no switchport SW2(config-if-range)# channel-group 1 mode on Step 3 – Assign IP Address to Port-Channel SW1(config)# interface port-channel 1 SW1(config-if)# ip address 192.168.1.1 255.255.255.0 SW1(config-if)# no shutdown SW2(config)# interface port-channel 1 SW2(config-if)# ip address 192.168.1.2 255.255.255.0 SW2(config-if)# no shutdownAnswer the question below
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