How can i active multilink on same switch.

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Mar 31st, 2007
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I have three fibers coming from the different different locations on the same location. I want to active three links. When one link is goes down the network is up from the other link.

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royalblues Sat, 03/31/2007 - 04:14
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i dont know whether i understood your problem correctly

First of all multilink is not possible on ethernet interfaces.

Bundling at layer 2 can be achieved by etherchanneling using Pagp & LACP, but you cannot achieve the same between different chassis

Etherchannel across chassis is only possible in 3750 stack configuration

HTH, rate if it does


mparekh Sat, 03/31/2007 - 06:04
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Just to get it straight - you have three fibers coming in from three different location and you want all 3 links active and backing each other?

If this is the case i recommend if possible (if you have layer 3 switces) to use some sort of routing protocol. If one link goes down the routing protocol (ie eigrp or ospf) will reroute the network traffic over the second or third link. Layer 2 spanning tree protocol could also work but it would depend on how you have the switches at the 3 different locations connected to each other.

You can try etherchannel, the configuration varies depending on the switch model you are using.

I got the scenario wrong i recommend posting a diagram of your network.

Amit Singh Sun, 04/01/2007 - 21:39
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The original poster is using 2950/2960 L2 switches. You cannot create static route on a L2 switch.

Upendra: Please paste your network diagram. What exactly you are trying to achieve.Please mention all 3 sites connectivity.

At layer2 if you want to use one interface as a backup of other you can use Flex links. Flex links is an alternative to STP.

Note: STP on the ports gets disabled when you use STP.

Flex links is not supported on 2950 switches. Please let us know your network topology and we will let you the exact solution.

HTH,Please rate if it does.

-amit singh

Amit Singh Mon, 04/02/2007 - 03:19
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Hello Upendra,

In the diagram pasted, all the links by default will be active and STP will be running on the them. This is a pretty small topolgy and STP should take care of path redundancy. If you want you can configure RPVST+ for fater convergence time as oppose to the traditional STP.

Pagp/LACP ether-channel bundling will not work in the present scenario.If you have redundant links from each 2960's to 3750 switch directly then you can use ether-channel between the switchports to give you aggregate throughput and link redundancy.

Flex links can be used in this scenario but the problem will be there on the central 2960 which just above the 3750 in the digram. As this 2960 doesnot have any direct link to 3750 so configuing the active/backup link on this switch will be a little challanging.

My idea will be stick with RSTP and let it do the job for you.


-amit singh


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