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Flexlinks and EIGRP Stub Comparison

Hello:

I am wondering if anyone can point me in the direction of a Cisco document that discusses Flexlinks and EIGRP stub networks and which ones would be better for any given deployment.

Thanks in Advance,

Brad Olson

6 REPLIES
Hall of Fame Super Blue

Re: Flexlinks and EIGRP Stub Comparison

Brad

Perhaps you could expand on the requirements you are looking at or possibly the designs you have in mind.

Flexlinks and EIGRP stub are 2 very different things and so it's a little unclear why you think it is an either or solution ie. either use flexlinks or use EIGRP stub ?

Jon

New Member

Re: Flexlinks and EIGRP Stub Comparison

Jon:

Thank you for the reply.

The main thing we are after is access switch redundancy. The LAN is a mix of 3550 and 3560 switches connecting to a 4507.

My main concerns in using one over the other are convergence times and ease of deployment in a 24/7 environment. Another concern is losing my VTP domain to the access switches for WAPs and things of the sort that I have VLANd off currently.

Thank You,

Brad

Hall of Fame Super Blue

Re: Flexlinks and EIGRP Stub Comparison

Brad

Still not entirely clear.

If you use EIGRP stub in the access-layer switches then that suggests you are routing in the access-layer ie. the L3 vlan interfaces that act as default-gateways for the clients are on the access-layer switches. So VTP to the access-layer switches would not be relevant in this scenario.

If the L3 vlan interfaces that act as default-gateways for the clients are on the 4500 then EIGRP stub is not applicable and you would use either flexlinks or etherchannel from the access-layer switches to the 4507.

Jon

New Member

Re: Flexlinks and EIGRP Stub Comparison

Jon:

Thanks again. I apologize for not being able to vocalize what I am trying to accomplish. I am not very experienced in this scenario.

A consultant currently set up one of the buildings using EIGRP stubs for failover in groups of 4. So, per two groups of switches there are 2 3560's connected to the 4506 and there are 2 3550's in between that are interconnected to each other.

It is my understanding that this was done for both redundancy and VLAN segmentation. In other words, the VLANs only live on the access layer switches that are connected together with a separate subnet on an IP addressed port on the 4506.

Does this make a little more sense? I will try and get a few sanitized configs up later today if I am still not being clear.

Thanks,

Brad

Hall of Fame Super Blue

Re: Flexlinks and EIGRP Stub Comparison

Brad

No need to apologize.

Are you saying there are 2 3560 switches that the connect to a pair of 3550 switches which connect to the 4500. It's this line that is a bit confusing -

"So, per two groups of switches there are 2 3560's connected to the 4506 and there are 2 3550's in between that are interconnected to each other."

Flexlinks works at L2. So it really depends on what the uplinks from the access-layer to the 4500 are. If the vlans live on the access-layer switches then you are routing in the access-layer. As Giuseppe noted, traditionally this would then mean that the uplinks from the access-layer to the 4500 would be L3 routed links but they don't have to be ie. they could be L2 and maybe this is where the flexlinks bit comes in.

If they are L2 i would recommend changing them to L3 etherchannels as this would then fit with the routed access-layer campus design.

Perhaps if you could post a topology digram for one of the failover groups showing connectivity to the 4500 and some IP addressing.

Jon

Hall of Fame Super Silver

Re: Flexlinks and EIGRP Stub Comparison

Hello Brad,

but EIGRP stub is a L3 feature and Flexlinks are an alternative to STP for managing redundant links at layer2.

So using EIGRP stub means moving to a routed access layer with vlans confined in a single switch and L3 uplinks.

Edit:

Jon I didn't see your answer but we are saying the same.

Hope to help

Giuseppe

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