Dual Homing (Link Aggregation) Servers

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Sep 28th, 2006
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Hi,


I have been following the document

http://www.cisco.com/application/pdf/en/us/guest/netsol/ns304/c649/cdccont_0900aecd800ea162.pdf


We are moving our network to a data center this is why I am reading this document. I have found an interesting point in this doument.

Page 18 (Link Aggregation Modes) states:

"The main disadvantage of the link aggregation modes is that all team members need to be connected to

the same access switch which is a single point of failure."


See my attached diagram.


If you look I have proposed a way of getting around the Link Failure by using a Cisco 3750 switch. If I use this switch am I right in saying that I have overcome the single point of failure while still preserving the ability to use Gigabit Etherchannel between the server and access layer switch?


Any comments will be rated.


Thanks




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Aaron Harrison Thu, 09/28/2006 - 06:59
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Hi


Yes - you can do etherchannel on a stacked set of 3750s to work around the issue highlighted.


Versions SEE and above support dynamic aggregation protocols, earlier ones you need to configure with


channel-group XX mode on


Regards


Aaron


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gavin.mckee Thu, 09/28/2006 - 07:15
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Aaron


When you say that version SEE and above support dynamic aggregation protocols what exactly do you mean? The 3750G switches I would be ordering to do this job would most likely have the EMI image. I just assumed that dynamic aggregation protocols would be supported.


Thanks



Gavin

Aaron Harrison Thu, 09/28/2006 - 07:25
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Sorry - current version is 12.2(25) but they have a suffix e.g.


12.2(25)SEB2

12.2(25)SEB3

12.2(25)SEB4

12.2(25)SED

12.2(25)SEE


etc...


The last shipping version i saw was a 12.2(25)SEB4 I think, so you'd need to upgrade to 12.2(25)SEC or later to take advantage of what's listed in the release notes linked below as 'cross-stack etherchannel'...


http://www.cisco.com/en/US/products/hw/switches/ps5023/prod_release_note09186a00804cc6aa.html#wp89520


I've configured Etherchannel on earlier versions, it works, you just don't get LACP/PAGP...


Aaron


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gavin.mckee Thu, 09/28/2006 - 07:51
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thanks for that, i'll have a look into doing cross stack etherchannel.


Gavin

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