Etherchannel on Cisco IOS Catalyst Switch

Lessons Discussion
1

This topic is to discuss the following lesson:

2

Hi, Rene. Thanks for info. What if you add note about pagp silent/non-silent submode? Thanks.

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Hi Andy,

Here’s an example for PAgP silent/non-silent:

Rene

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hi Rene, i can’t understand what’s different between PAgP and LACP, why cisco created PAgP? does it has some pros?

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Hi Yevgeniy,

Good question. Etherchannel was originally invented by a company called Kalpana in the 90s. Cisco bought the company in 1994 and released PaGP. Later in 2000, IEEE released an open standard version for Etherchannel (802.3ad) which is LACP.

Rene

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6

Hi Rene,

What is the benefit of etherchannel protocols if we can configure interface as etherchannel manually by setting the mode of etherchannel (on) in both side ? so why we need to set one side Desirable or Active and the other side Auto or Passive ?

1 Like
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Hi Hussein,

When you use PAgp or LACP the Etherchannel will only form when the settings match on both sides. If you use “on” then you can end up with a loop if the configuration of the interface doesn’t match on both sides.

Rene

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Hi Rene,

I confused because I will end up with a loop also if I use etherchannel protocols and that happen when the configuration of the interfaces doesn’t (Desirable - Auto) or (Desirable - Desirable) or ( Active - Passive ) or ( Active - Passive )!!!

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Hi Rene,

I confused because I will end up with a loop also if I use etherchannel protocols and that happen when the configuration of the interfaces doesn’t (Desirable – Auto) or (Desirable – Desirable) or ( Active – Passive ) or ( Active – Passive )!!!

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Hi Hussein,

When you use PaGP or LACP then the two switches will do some negotiation and form an etherchannel. When you use “etherchannel on” on one side and regular ports on the other sides then you can get loops. What went wrong with your etherchannel setup?

Rene

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Hi Rene,

Thank you so much I got the idea and I confused because I am using packet tracer but in real switch it’s work like you said

Thanks again.

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Hi Rene,

The max. physical interfaces can be up to 8 in creating an etherchannel. Is that 8 on one switch and 8 on the other switch, thus, forming 8 links? (so, if ports were 1 gig, the max. etherchannel can be as high as 8 gig etherchannel). OR is the max. 4 on each switch?

Thanks!
Joey

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Hi Joey,

It’s 8 ports on each switch so you can combine 8 links into one etherchannel. For example, 8 gigabit links will get you a single 8 gigabit etherchannel.

Rene

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Hi Rene,

We have 3850 switch and Symantec Backup Exec. We create nic teaming and etherchannel 4 interfaces. When we backing up the fileserver (For example) nic teaming never use 4 gigabit, only use 4 gigabit. When we copy a large amount files different sources we can see 3,5 gigbit. We want to see 4 gigabit for singlehost use which configuration can we use? can u help us?

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Hi Can C,

This will be a problem. The 3560 / 3750 (and I think the 3850) offer these load balancing mechanisms:

port-channel load-balance {dst-ip | dst-mac | src-dst-ip | src-dst-mac | src-ip | src-mac}

Since the source/destination is always the same, you will always use the same physical interface…no matter what load balancing mechanism you pick. You will only get the 4 gigabit bandwidth if you have multiple hosts on one side or if you can configure your application (backup exec in this case) to use multiple connections.

Rene

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Hi Rene,
2 questions for you:

  1. Let’s say that I have bound all my links using the Channel-group command. The logical port-channel 1 is automatically created.

I see that if you want to apply changes to all ports in the Port-channel at the one time, you can configure just the logical port-channel. Does that apply to parameters such as port speed, duplex etc. for example:

Switch(config)#interface port-channel 1
Switch(config-if)#switchport
Switch(config-if)#duplex full
Switch(config-if)#speed 1000
Switch(config-if)#switchport trunk encapsulation dot1q
Switch(config-if)#switchport trunk allowed vlan all
Switch(config-if)#switchport trunk native 99
Switch(config-if)#switchport mode trunk
Switch(config-if)#no shutdown
Switch(config-if)#end
  1. Can you create more than 1 PORT-CHANNEL between SW1 and SW2?

e.g. a port-channel 1 containing 8 links and a port channel 2 containing 8 links…

seamus

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Hi Seamus,

It applies to switchport settings and I think speed/duplex will also work, it’s possible though that the etherchannel will be torn down if you change the speed though. I’ll check this when I get back from my holiday :slight_smile:

Creating more than one port channel between two switches is no problem at all. The limit of 8 links is per etherchannel.

Rene

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I really don’t know how you do it but you really seem to simplify seemingly complex subject matter into graspable format.
I’ve entire chapter to finish reading but seems like reading your article alone covers it all.
Thank you so much.

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Thanks Navin, glad to hear you like it! I do my best to explain everything as simple as possible. Once you understand the basics it’s easier to learn all the “extras”.

1 Like
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I just checked, changing the speed/duplex on the port-channel interface will also copy this to the physical interfaces.