Flex Links vs. Backup command

Unanswered Question
Aug 18th, 2008


We are having two 6500 switches connected over one 10G link, and we are going to create an additional 10G link with Etherchannel and an additional four 1G links with Etherchannel to be used as a backup for the 10G Etherchannel.

We are trying to avoid the spanning-tree and we might be using Flex links feature.

My question:

What the difference between the Flex links and the normal backup command

Configuration sample:

Flex link:

Interface port-channel 1

switchport backup interface port-channel 2

Backup command:

Interface port-channel 1

backup interface port-channel 2

Any help would be appreciated…

I have this problem too.
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satish_zanjurne Mon, 08/18/2008 - 21:24

Flex Links provide link-level redundancy that is an

alternative to Spanning Tree Protocol (STP). STP is automatically disabled on Flex Links interfaces.

To configure the Flex Links feature, you configure one Layer 2 interface as the standby link for the link

that you want to be primary. With Flex Links configured for a pair of interfaces, only one of the

interfaces is in the linkup state and is forwarding traffic. If the primary link shuts down, the standby link

starts forwarding traffic. When the inactive link comes back up, it goes into standby mode.


1.One of the use of "backup interface" command is to put ISDN dialer interface or ISDN BRI interface itself as backup to the primary link.So that as soon as your primary link like T1/E1/DS0 goes down, ISDN will fire and you have backup link up, it will be configured alongwith delay command.

2.Other use of backup interface command is in ASA , but it only for VLAN interface.



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