Hi Rene,
You’ve confirmed my suspicion.
In stead of upgrading to a 10Gb link, would it not be easier to use routing, with EIGRP you have automatic load-balancing and L3 switches are more affordable. It also adds redundancy.
Best regards,
Hans de Roode.
Hi Hans,
For network devices that could be an option yes, L3 networks have some advantages over L2 networks…you don’t have to deal with spanning-tree, redundant links can be used instead of blocked and the convergence time is faster. For your end devices like a fileserver, you still have to deal with L2 interfaces (switchport).
Rene
Hi Rene
" Etherchannel will do load balancing among the different links that we have and it takes care of redundancy."
Load balance implies equal bandwidth distribution among the physical links. Would you agree that load sharing would be more appropriate, as equal bandwidth distribution is not always achieved due to the hashing algorithm?
Let me know. I appreciate your content, as it is always a reliable source for myself. Also, Nexus topics or ISE would be some a great addition if you are looking for new content.
-Mike
Hi Mike,
Load sharing might make more sense yes. If we could do per packet round robin then it would be more like load balancing since we could evenly share the load on all physical links.
With the hashing algorithms we can use for Etherchannel it can be hard to get above the bandwidth of a single physical link when there’s only a few sources/destinations. It’s similar to a highway, we can add more lanes but that doesn’t mean we can always drive faster 
Once i’m done with all R&S content I’m going to work on Nexus material, there’s quite some demand for it
Rene
Goede Morgen Rene,
I re-created PAGP Etherchannel on 2 x 2960 X real lab based on example above but from your Vault Lab i…e blind. First I converted each of the 4 x physical interfaces to trunk mode then i configured using the interface range command two physical interfaces on sw1 to actively form the etherchannel :-
interface GigabitEthernet1/0/13
switchport mode trunk
channel-group 1 mode desirable
!
interface GigabitEthernet1/0/14
switchport mode trunk
channel-group 1 mode desirable
I then did the same on SW2 :
interface GigabitEthernet1/0/13
switchport mode trunk
channel-group 1 mode auto
!
interface GigabitEthernet1/0/14
switchport mode trunk
channel-group 1 mode auto
BUT the etherchannel did NOT come up so it stayed down until i did a shut and no shut on the P01 interface … can you tell me is this normal or what happened ? many thanks in advance
PRETTIGE DAG
Will
Hi Will,
This can happen yes. Sometimes it does come up, sometimes it doesn’t. Doing a quick shut/no shut on the PO interface is quick way to “refresh” all interfaces.
Rene
Would you use Etherchnnel between two L3 switches in the distribution layer (not utilizing/enabling VSS)?
Hi Jason,
If you can use VSS then yes, it’s a good idea. Only the higher end switches support it though.
Rene
Hi Rene,
You content is very rich dear:) I have one questions , If we use both end same like…
Is there any issue on technically ?? I use Active Ative and PO is running. Also Some Router Support LACP/PAgP.Could you please add the topic .Many Thanks
br/
zaman
Mohammad,
There are only a couple of combinations that will work if you set both ends as the same:
PAgP
Desirable - Desirable
LACP
Active - Active
Manual (not recommended)
On - On
Any other combination of having both sides set the same will fail to form an Etherchannel. This is because with both Auto and Passive, neither of those modes send out packets to create an Etherchannel. Instead they are only listening for inbound requests to create an Etherchannel. If you have two sides that are both listening, but not sending, no communication will actually happen.
Dear Andrew,
Many Thanks…
So If we set both end active-active or Desirable=Desirable then both side will ask for create Etherchannel to far end and no one will respond right and also that behavior will creat any problem???
I a have tried the Load Balancing topology with GNS3 by setting both end src-mac and see from my capture its taking all path from SW1 and SW2 when send pinging from MAC:AAA TO MAC:EEE and revert .Need more clarification on it.
br//
zaman
Both sides being set to Active-Active or Desirable-Desirable will result in a correctly functioning Etherchannel. Each side is aware that the other wants to create one, and it doesn’t bother them that each side is asking proactively for it.
I am not following what you are asking in your second question? Are you saying that the etherchannel you created is not balancing traffic correctly? If so, we will need more details (preferably the configuration you used to create it).
Hi Rene and Andrew,
I have configured a L2 etherchannel by using the following commands
On the 1st switch, i issue
The 2 lines went up and the port-channel got created and up.
This was done on only 1 side of the switch but show etherchannel summary show the PO1 (SU) – layer2 and in use.
Subsequently, i went to setup the same on the 2nd switch.
Q1) My question is , how do we verify that the port-channel connectivity between the 2 switches are really working (given that it turn ups even only when 1 side of the switch is configured).
Q2) I have configure src-dst mac load-balancing, but other then using “test etherchannel load-balance”, is there anyway way to see the traffic distribution between the 2 interface/lines on the switch ?
I do a show int fa0/23; and show int fa0/24, trying to a get baseline of the current traffic on both interfaces before sending some packets out, but the output packets on both interfaces jumps all the time before i even actually send the actual traffic out.
How do i verify that both links are actually “used” ?
Regards,
Alan
Wonderful job
Hi Alan,
First, I want to make sure you are aware of a great lesson available on Etherchannel Troubleshooting. Why not give that lesson a read-through, and see what you can learn from it? If you still are wondering about verification after that, feel free to post, and Rene or I will answer you right away!
I do want to give you one bit of caution … Generally, with technology, but Cisco in particular, there is a cautious attitude that any feature that is “auto …”, you outta not use it Etherchannel, however, is one big exception to this. It is highly recommended that in a real world design you use LACP (or PAgP if you have all Cisco equipment) as opposed to “ON.” It is very easy for something to go wrong in an Etherchannel setup, and with “ON” you have no protection against frame looping. I have had this personally happen to me!
The other nice thing about using LACP or PAgP is that you won’t be fooled by just one side of the Etherchannel coming up as you experienced. Only if both sides agree and pass all their internal checks will the Port Channel come. So this would be a good indication that the Channel-Group is actually functional.
Dear Rene,
Please correct me if I am wrong …
If we use Negotiation protocol then both end & Local(Between Links) configuration must be identical of below parameter :
Duplex has to be the same.
Speed has to be there same.
Same native AND allowed VLANs.
Same switchport mode (access or trunk).
If we dont use Negotiation protocol then only local (Between Links) configuration must be identical , right ??
br//
zaman
Dear Zaman,
That is correct: speed/duplex/vlans/switchport mode should be the same on both ends for negotation to work.
Without negotiation, these parameters are not checked so you can configure the Etherchannel anyway. I would still recommend to keep all parameters the same though.
Rene
19 posts were merged into an existing topic: Etherchannel on Cisco IOS Catalyst Switch
Hlw Rene,
Thanks a lot, Rene, you are amazing !
One more Questions…
What’s the necessity of the command “channel-protocol lacp” ??
br/
zaman
Hi Zaman,
It is used to restrict anyone from using non-LACP commands. Here’s an example:
You can use the channel-protocol command to restrict anyone from selecting a mode that is not applicable to the selected protocol
SW1(config)#interface GigabitEthernet 0/1
SW1(config-if)#channel-protocol lacp
SW1(config-if)#channel-group 1 mode ?
active Enable LACP unconditionally
auto Enable PAgP only if a PAgP device is detected
desirable Enable PAgP unconditionally
on Enable Etherchannel only
passive Enable LACP only if a LACP device is detected
SW1(config-if)#channel-group 1 mode auto
Command rejected (Channel protocol mismatch for interface Gi0/1 in group 1): the interface can not be added to the channel group
SW1(config-if)#channel-group 1 mode desirable
Command rejected (Channel protocol mismatch for interface Gi0/1 in group 1): the interface can not be added to the channel group
SW1(config-if)#channel-group 1 mode on
Command rejected (Channel protocol mismatch for interface Gi0/1 in group 1): the interface can not be added to the channel group
All non-LACP commands are now rejected.
Rene