Layer 3 Etherchannel on Cisco IOS Switch

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Hi rene, I am trying to configure a layer 3 etherchannel, the new version of GNS3 but once configured everything, I can not do ping between the two portchannel, I appreciate your usual help, I’m using the version that uses the IOU of a virtual machine built to GNS3

Hi Catalino N,

I think this might be an IOU problem, I’ve read before that it accepts the configuration but that you can’t send any traffic through L3 etherchannels.

When you use the show commands, everything looks fine?

Rene

Hi Rene ,

What s the difference between a l2 and l3 etherchannel ? Beside the fact that a l3 port channel has a IP address .

Do they difference in the way traffic is load balance across the links or ?

Hope to hear your advice soon !

Hi Alan,

It’s exactly the same as the “switched port” and the “routed port”. The L3 etherchannel has IP addresses, the L2 etherchannel has vlan(s). All the other stuff like load balancing is the same.

Rene

Hi Rene,

q1) in your example above, for L3 etherchannel setup

q2) can we have an etherchannel of different type at each end of an etherchannel link ?
(E.g. L2 switch to Router? )
L2 on the switch, L3 on the router

q3) for L3 etherchannel, is load balancing different from L2 etherchannel (e.g. L3 loadbalancing is using SRC / DST IP ?), can L3 etherchannel load balance using MAC ?

q4) From you example, i believe we can have different load balance mode on each end of an etherchannel right ?

Hope to hear from you soon.

Regards,
Alan

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 use a different load balancing method on each side.

Rene

Hi Rene,

Thanks for the concise reply.

On 2) Is it not a norm to setup etherchannel from switch to router ? I am just wondering if i am to have multiple switches doing etherchannel to a core switch, but if the core switch would have just 1 physical link up to the router, isn’t that the choking point for all the high availability and bandwidth among the switches ?

Regards,
Alan

Hi Alan,

It depends on your WAN connection. On your LAN we use gigabit links to desktops and perhaps 10 gigabit links (or etherchannel with gigabit) for all internal traffic. If your WAN link is only 100Mbit then that’s your bottleneck.

Rene

Hi René,

Thank you for your excellent book. But concerning this lab, i am curious to know why this does not work for me. I have exactly the same configuration. May be you use a real switch.

For me i use a Cisco Iou layer L2 switch. can you give me some idea? I am confuse.

Thank you again

Paul

Hi Paul,

I used real switches for this. I think the support for Etherchannel in some of the L2 IOU images might have some bugs.

Since a few weeks I’m using VIRL, just tried PAGP in it and that worked without any issues.

Rene

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: PAgP not enabled on the remote port.

although it is configured on both switches.

Would appreciate any advice regarding how you got it to work.

thank you,

Dirk

Hi Dirk,

I also experienced this a few times. I didn’t install anything nor rebooted my VIRL server. I’m running the latest version.

I’m not exactly sure what fixed it for me but I think a “shut/no shut” on the PO interface didn’t solve it. After removing the PO interface and adding it again it started to work.

If you want, I can check it again.

Rene

Rene,

Hello, I have a question on models of switches. There are Lan, IP, Enterprise versions, if I want to use the Hot-Standby option I assume the Lan version won’t have that capability. Which versions is this feature supported?

Thanks,

Chris

Hi Chris,

You can find this in the Cisco feature navigator.

Try this:

  1. Select “search by feature”

  2. Search For: “standby”

  3. Select HSRP on the right side.

  4. On the Release/Platform Tree below select “Platform”. Choose your router/switch

  5. The search results will show you what IOS images support it. For example, here are some results for the 1941 router:

15.2T	15.2(1)T2	ED	No	1941	UNIVERSAL (DATA & SECURITY)
15.2T	15.2(1)T2	ED	No	1941	UNIVERSAL (SECURITY)
15.2T	15.2(1)T2	ED	No	1941	UNIVERSAL (DATA)
15.2T	15.2(1)T2	ED	No	1941	UNIVERSAL (IP BASE)

Hope this helps!

Rene

Rene,

Thanks that helped, looks like I need the IP Base or IP Services model for this to work.

Thanks again,

Chris

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?