Cisco 2960-24TT-L uplink port question

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Apr 7th, 2010
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Can the uplink ports be used for resilience? I mean can I connect Uplink 1 to a core stack and can I then connect Uplink 2 to the same core stack without creating a loop? Can the uplinks be configured as trunks?

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Jon Marshall Wed, 04/07/2010 - 05:08
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goldiethedog wrote:


Can the uplink ports be used for resilience? I mean can I connect Uplink 1 to a core stack and can I then connect Uplink 2 to the same core stack without creating a loop? Can the uplinks be configured as trunks?


They can be configured as trunks. And if you want resiliency then simply configure both uplinks as a L2 etherchannel so neither physical link would be blocked.


So you would have a L2 etherchannel trunk link. See this link for details -


2960 etherchannel


Jon


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goldiethedog Wed, 04/07/2010 - 06:06
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Thanks for the reply Jon.


I'm not sure why the etherchannel would be advantageous over just trunks though?

Jon Marshall Wed, 04/07/2010 - 08:14
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Paul


Because STP sees an etherchannel as one link. So the 2 physical links are both forwarding with etherchannel and if one link fails the forwarding will continue on the other link.


If you configure 2 individual  trunks one allowing the same vlans one link will be blocked by STP so you can only use one link for forwarding and if it fails STP then needs to unblock the other link.


This is why etherchannel trunks are used to interconnect switches.


Edit - there is nothing stopping you using 2 trunks if you want it's just not the most efficient way of doing it.


Jon

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