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Community Member

Load sharing and Redundancy - Scenario

Hi,

I have three links on a new site with unequal bandwidth, is it possible to combine all to have load sharing and redundancy

Link#1 Point-to-Point = 4MB ( Ethernet )

Link#2 Point-to-Point = 2MB ( Fiber )

Link#3 Point-to-Point = 6MB ( Ethernet )

Can someone share steps how to achieve it.

Thanks

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Super Bronze

Re: Load sharing and Redundancy - Scenario

If you're only unfamilar with EIGRP configuration for unequal costing, this might help: http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009437d.shtml

8 REPLIES

Re: Load sharing and Redundancy - Scenario

The best routing protocol for that would probably be EIGRP. That allows load balancing over unequal cost links, you just need to make sure variance is set - I wuld start with variance set to 4.

Super Bronze

Re: Load sharing and Redundancy - Scenario

As Paul suggests, EIGRP can direct number of flows to each link based on its bandwidth. However, unless all flows use equal bandwidth, don't be surprised to see actual link loading not balanced.

If EIGRP isn't an option, for routing protocols that support equal costed multiple paths, e.g. OSPF, you might "lie" to the protocol to have it use all 3 of your paths. (Since your bandwidths aren't "too" far apart, this could be an option for you.)

Lastly, Cisco routers, in their later IOS versions, support a new technolgy, OER/PfR. This technology can dynamically load balance, but there are many restrictions to using it.

In theory, pehaps the best combination would be EIGRP to initially direct flows per link bandwidth and OER/PfR to issure actual load is balanced.

Community Member

Re: Load sharing and Redundancy - Scenario

Hi,

Thanks for your input.

I have attached the network diagram, can you help with steps to configure Eigrp to load balance the link.

Can you help me to understand if I can use EtherChannel for this scenario

Super Bronze

Re: Load sharing and Redundancy - Scenario

Your diagram shows OSPF already being used? Although it's possible to use EIGRP across the links, if you're already using OSPF across them, you might just set each link's OSPF cost the same and see how that works for you.

Concerning Etherchannel, I think(?) like interfaces are required.

Community Member

Re: Load sharing and Redundancy - Scenario

can you give me steps to configure EIGRP.

Will EtherChannel help in my scenario.

Hall of Fame Super Gold

Re: Load sharing and Redundancy - Scenario

Do you want to do yourself a BIG favor?

Ask your SP to consolidate all links in one, and get a good SLA for it.

You will need a lot of aspirine otherwise.

Super Bronze

Re: Load sharing and Redundancy - Scenario

If you're only unfamilar with EIGRP configuration for unequal costing, this might help: http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009437d.shtml

Hall of Fame Super Gold

Re: Load sharing and Redundancy - Scenario

Don't forget to update us on how EIGRP unequal sharing works for you -- especially when offered traffic is near to the sum on BW.

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