Layer 3 Etherchannel on Cisco IOS Switch

In a previous lesson I explained how Etherchannels work and how to configure them, but I didn’t write about layer 3 Etherchannels before. In this lesson, I’ll show you how to configure them.

A layer 3 etherchannel is similar to an interface on a router. The switch won’t “switch” traffic on this interface but route it. Because it’s a layer 3 interface, we configure an IP address on it.

I’ll be using two switches for this:

Etherchannel L3 Addresses

Before we configure the port channel settings you need to make sure that all interfaces have the exact same configuration. Once you use the channel-group command, the port-channel interface will automatically inherit all settings from your physical interface. If you forget to run the no switchport command on an interface, your etherchannel will be layer 2 instead of layer 3!

Having said that, let’s configure our switches:

SW1(config)#interface range fastEthernet 0/1 - 2
SW1(config-if-range)#no switchport
SW1(config-if-range)#channel-group 12 mode on
Creating a port-channel interface Port-channel 12
SW2(config)#interface range fa0/1 - 2
SW2(config-if-range)#no switchport
SW2(config-if-range)#channel-group 12 mode on
Creating a port-channel interface Port-channel 12

This creates our Etherchannel, we can verify our work like this:

SW1#show etherchannel 12 summary 
Flags:  D - down        P - bundled 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

        M - not in use, minimum links not met
        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
12     Po12(RU)         -        Fa0/1(P)   Fa0/2(P)

Above you can see that our port-channel 12 interface is layer 3 and it’s operational. Just like any other layer 3 interface we can configure an IP address on this port-channel interface:

SW1(config)#interface port-channel 12
SW1(config-if)#ip address
SW2(config)#interface port-channel 12
SW2(config-if)#ip address

Let’s see if that works:

We're Sorry, Full Content Access is for Members Only...

If you like to keep on reading, Become a Member Now! Here is why:

  • Learn any CCNA, CCNP and CCIE R&S Topic. Explained As Simple As Possible.
  • Try for Just $1. The Best Dollar You’ve Ever Spent on Your Cisco Career!
  • Full Access to our 739 Lessons. More Lessons Added Every Week!
  • Content created by Rene Molenaar (CCIE #41726)

559 Sign Ups in the last 30 days

100% Satisfaction Guaranteed!
You may cancel your monthly membership at any time.
No Questions Asked!

Tags: , ,

Forum Replies

  1. Hi Alan,

    1. This was an error which I just fixed. On both ends it should be “no switchport”. There’s two ways how you can create the Etherchannel, you could first manually create the port channel interface and add the physical interfaces or you can do what I did. If you assign physical interfaces to a non-existing port channel then it will be automatically created.

    2. Hmm I haven’t tried this but I guess it could work. It’s similar to connecting a router interface (L3 routed port) to a switch (L2 switchport).

    3. Load balancing is the same for L2 and L3 and you can

    ... Continue reading in our forum

  2. Hi Rene, you mention above that you have been able to get L3 PAgP working with VIRL. When I try, the etherchannel is always suspended at both ends. See output of ‘show etherchannel summary’ command.

    Group Port-channel Protocol Ports
    1 Po1(RD) PAgP Gi0/1(s)

    I’ve tried ‘sudo vinstall bridge’ & restarting my VIRL vm as recommended on the VIRL discussion pages, however the problem persists and I continue to receive the log message:

    *Nov 2 10:48:04.907: %EC-5-L3DONTBNDL1: Gi0/1 suspended:

    ... Continue reading in our forum

  3. Hi Rene,

    In campus LAN of multi building LAN in hub and spoke setup
    Each spoke location runs as much as layer 3
    There are few services can’t create local layer 3 subnet e.g. centralized wireless setup
    In this case uplinks between spoke and hub need to carry both L2 and L3 network
    Since a port can either switched or routed port - this means to carry both the l2 and l3 - there should be 2 active uplinks?

  4. Thanks Rene for your response,

    Probably WLAN is not good choice of comparing to extended the network since CAPWAP is L3

    If you refer to this correct answer in this URL

    Assume a access switch (as1) gig0/1 uplink to distribution switch (ds1) gig0/2

    as1 switch configuration

    interface GigabitEthernet0/1
     description ** Uplink to ds1 **
     switchport mode trunk
     switchport trunk encapsulation dot1q
     switchport trunk allowed vlan 10
    interface vlan 250
     ip address 192.168.10.
    ... Continue reading in our forum

  5. Hi Santhosh,

    In this example you’ll have L2 interfaces from the access switch to the distribution switch with SVI interfaces for L3 so yes, you’ll have L2/L3 traffic over the same link. It works but it’s not what we normally do.

    With a design like this where we use trunks from the access layer to the distribution layer we normally don’t use SVI interfaces on the access layer. You can stick to cheaper L2 switches for the access layer and let the distribution layer do the routing…that’s where you configure SVI interfaces.

    Let me give you two examples for a typica

    ... Continue reading in our forum

61 more replies! Ask a question or join the discussion by visiting our Community Forum