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TOPIC: A few switching questions

A few switching questions 14 years 2 weeks ago #7072

What is the difference between trunking and channeling and which would be used in this situation?

I have a 2948G switch and want to connect it to the core 6509 with multiple GBIC fiber links. This should give the users more bandwidth and failover capability in case one fiber link goes down. Can anyone show me a sample config?

*.CX team the labs look like they are going to be great, keep up the fantastic work.

Re: A few switching questions 14 years 1 week ago #7221

Truncking is normally used with vlans to allow two or more vlans to connect to some other device such as a printer. Think of a tree, where the leaves are the computers and the brach is the vlan and the trunk is the commun comunication path. So that if one leaf on one brach wants to talk to another leaf on another branch, it has to do it thru the trunk.

Maybe someone else can explan the purpose of channeling, and how it works.

Re: A few switching questions 14 years 1 week ago #7236

*patiently waits for Chris*
"He who breaks something to find out what it is, has left the path of wisdom."

Gandalf the Grey

Channeling 14 years 1 week ago #7248

I'm setting up a pair of Cisco switches at the moment. EtherChannel is what they call the arrangement of aggregating the bandwidth of two or more links between switches to provide a fatter pipe. You also get resilience since if one of the member links dies the rest carry on. Confusingly though, the channel works because the links are set up to use 801q trunking. We may be brewing terminology soup here

(waits patiently for Chris...)

Re: A few switching questions 14 years 1 week ago #7253

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Sorry for the delay in this post, but you see..... the word 'Cisco' was absent from the thread's topic, so I missed it :)

As TheBishop so correctly noted, the correct 'feature' you need to use it Etherchannel, rather than Trunking. Trunking is covered in our VLAN topic with much detail, so please refer to that if you require more information on the topic.

Etherchannel as a neat feature that allows you combine multiple Fastethernet interfaces between two switches or a switch and a massive router/switch e.g 4500, aggregating the available bandwidth to provide a fault tolerant super highway link.

If one or more of the aggregated links decides to fail, then you don't need to worry as the rest will automatically take care of the traffic. You should also note that you are able to perform load balancing with EtherChannels, but I won't get into any details at the moment.

Limitations: In order to successfully create an EtherChannel, you must use FastEthernet or Gigabit Links. In addition, all links in the EtherChannel must be that of the same speed. You can't combine 100Mbit and 1Gig links!

Lastly, you can aggregate a maximum of 8 links for each EtherChannel!

So how do you create these EtherChannels ?

The whole theory behind EtherChannels is quite big, but basically two different ways: 1) Layer2 Etherchannel Interfaces 2) Layer 3 Etherchannel Interfaces.

Assuming Layer2 EtherChannels, For each interface that will be part of the Etherchannel, enter the following commands:

[code:1]configure terminal
interface <interface-id>
switchport mode access/trunk vlan-id (if you plan to use the channel for one network -no trunking, then use 'access')
channel-group <number>mode auto
copy running-config startup-config[/code:1]

I'll try and post some more information, but I must run because I'm already late for a meeting!!!

Chris Partsenidis.
Founder & Editor-in-Chief
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