Yeah, that makes perfect sense. Although using an EC while having one link as standby (thus not using that link nor the load-balancing that EC offers) seems quite rare to me these days. I can’t think of many scenarios where this would be used.
A quick question, though. Is it necessary to have just two links in the EC? It’s not a requirement but I suppose that it makes sense to only use it with 2 since the design includes one link forwarding and one link idling.
Yes, I agree with you for the most part. There are other solutions that would probably be better to use for such redundancy. Even setting up an EtherChannel statically would probably be a better choice in many situations. With static EtherChannel, if a physical link fails, the rest of the links will continue to function without disruption. I guess one particular use case is if you have configured a switch to connect to two NICs on a server using LACP. Then using fast switchover is a good idea.
It’s not mandatory in that you can configure an LACP EtherChannel with more than two links and configure fast switchover. However, it is recommended by Cisco that fast switchover be used with only two physical links in the LACP portchannel.
a question please i have configured the layer 3 etherchannel on 2 layer 3 switches using packet tracer , the configuration is valid i am able to ping between the 2 ports , but i added a pc to each end and i am not able to do a ping between them , the PCs and the layer 3 addresses on the switches are on the same ip + subnet ,adding a picture below , if you could explain me what is not right it will be great thank you in advance
By definition, if you have a layer 3 Etherchannel link, the link between the two switches constitutes a single subnet/broadcast domain because by definition, an L3 Etherchannel link will have an IP address assigned to each end of the link. That means that the PCs must be configured to be on separate subnets. So having all devices on the same IP addressing subnet would not work.
In your diagram, each L3 switch must act as a router, and must have routing configured so that the two PCs will be able to reach each other.
Since you have correctly configured the L3 Ethernet link and you have tested it, to make it your topology work you must ensure the following is also configured:
Assign PC1 and PC2 to two separate subnets
Create a VLAN interface on each switch that will act as the default gateway for each PC
Configure the PCs with the appropriate default gateway
Ensure that each L3 switch has routing information about how to reach the subnet of the remote PC
Try it out and let us know your results. Let us know if we can be of any further help as well!
I understand now. Yes, it took me a couple of times to read your answer, but I understand each port that is L3 is a broadcast domain of its own. I got it. Thank you so much.
