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New Member

Load Balance and failover over 2 lines.

We have 2 x Cat 6509 with Sup720 and are running Native IOS.

On Switch A, we have a 1GB link configured as an access link on Vlan 2 to DR site connected to a Cat 3550

On Switch B, we have a 1GB Link configured as a trunk to the same DR connected to another Cat 3550

We configured devices to be in VLAN 2 as we want them to use the 1GB link. And the 2nd 1GB link is a logical extension of our main site.

Now, I want to configure these 2 x 1GB link so that they now act as failover as well as Load balancing.

1. How do I do this?

2. Will I need to move the 1GB link on Switch A to switch B

3. Should I configure the Switch A link also as Trunk?

Please help.


New Member

Re: Load Balance and failover over 2 lines.

Do your 3550s run EMI or SMI? If they run EMI, why not run dynamic routing protocol between the 3550s and the 6500s? OSPF would be a good one to use, if you have hierarchical IP addressing. If your addressing is not hierarchical, then use EIGRP.

Other than this, the only other possible way I can think of is GLBP (

Prior to GLBP, you could also have used HSRP. But it's a bloody nuisance to configure, 'cuz you need to configure two different HSRP groups for the same pair of switches, then manually assigning different hosts/PCs to use different default gateways. As I said, bloody nuisance.


New Member

Re: Load Balance and failover over 2 lines.

Thanks for your answer. We actually use EIGRP.

I have had a look at the link and it does not support Cisco 6509.

Is there a document that can put me through how to do your second option with the HSRP as we also use HSRP.

Thanks for your help

Cisco Employee

Re: Load Balance and failover over 2 lines.

If we move both links to either of the switches, we can configure an etherchannel and thus providing aggregated bandwidth along with load-balancing and resiliency. We just need to ensure similar configuration on both ends.

Please see:

Please post as applicable.


New Member

Re: Load Balance and failover over 2 lines.

Thanks. So this means I have to have both link on the same switch.

Is it possible I can have the link on different switches and still configure for load balance using EIGRP?

New Member

Re: Load Balance and failover over 2 lines.

What is the IOS image running on your 6509? It doesn't make sense that 6509s running IOS does not support EIGRP. We have a couple of dozens of these running EIGRP without any problems. In fact, within the corporate environment, 6509 is positioned as the flagship product, which usually means support of anything that Cisco wants to do. Even MPLS (although MPLS support on 6500's is apparently not as extensive as its sister/brother, the 7600s).

Cisco Employee

Re: Load Balance and failover over 2 lines.


Yes, we would have to move the links onto the same switch and configure them identically, exsame speed/duplex,same vlans forwarding,same port configs etc.

It would give you an added advantage of aggregated bandwidth apart from load-balancing and failover. Moreover, it can be a L3 or L2 port-channel.


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