Flex Links

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Jul 23rd, 2009
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I want to implement a backup link between switches without enabling STP. I'm looking for something similar to Flex Links, but, to use Flex Links, the 2960 switch must be running the LAN Base Image, and the switches that I want to configure are running the LAN Lite Image.

Do you know something similar to Flex Links that I can use with Catalyst 2960 Lan Lite image switches?

Thanks in advance.

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Roman Rodichev Thu, 07/23/2009 - 05:18
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Is it between the same two switches? Can you use etherchannel?



cdelafuente31 Thu, 07/23/2009 - 05:50
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I cannot use etherchannel. The link is not between the same two switches. One link connect to a switch and the backup one to an bridge/access point.

Thank you for the answer.

cdelafuente31 Thu, 07/23/2009 - 22:49
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Because the backup path will be connected to a 1300 wireless bridge. I've atthached a picture with the topology.

I don't wan to use STP because I want to avoid that, due to a topology change, the STP blocks the Switch B port that is connected to the AP-B. If this port is blocked, Switch D will lost the connection too.

Roman Rodichev Fri, 07/24/2009 - 10:23
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AP-B treats those two bridge links as two separate VirtualDot11 interfaces each with its own STP state. Depending on which switch is a root bridge, you can get AP-B in AP-C in blocking state, and all other paths in forwarding. If you make switch A a root bridge and all wired links are the same cost, you'd have AP-B or AP-C block that APB-APC link, and APB-APD would be forwarding.



vinodmehrag Tue, 03/23/2010 - 00:25
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Can you please tell me how to configure flex link between 2 2960 switches.

primary link should be on switch1 and backup link should be on switch2.

Your help is greatly appreciated.



cdelafuente31 Tue, 03/23/2010 - 01:29
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A simple example of flexlink is:

Switch# configure terminal
Switch(conf)# interface gigabitethernet0/1
Switch(conf-if)# switchport backup interface gigabitethernet0/2
Switch(conf-if)# end

In this case, when the gigabitethernet01 (the active link) goes down, the gigabitethernet0/2 will forward traffic.
But, when the active link goes up again, it will not preempt the backup link (the backup link will forward traffic until it fails).

To avoid this, You can configure preemption:

Switch# configure terminal
Switch(conf)# interface gigabitethernet0/1
Switch(conf-if)#switchport backup interface gigabitethernet0/2 preemption mode forced
Switch(conf-if)#switchport backup interface gigabitethernet0/2 preemption delay 50
Switch(conf-if)# end
For more information, you can access this link:
Best regards,

vinodmehrag Tue, 03/23/2010 - 03:07
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Thanks for the reply.

But I am using 2 different switches.

Primary link will be on first switch and backup link will be on second




On Tue, Mar 23, 2010 at 1:59 PM, cdelafuente31 <


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