EIGRP maximum-paths

[prashant]

Hi,

Can any one explaine me why we are using maximum-paths commnd in EIGRP. What is the actual use. If i use what will happen and what will effect.?

I know this is use for Load balancing purpose but how EIGRP do the load balancing.

In which condition i can use maximum-paths in EIGRP.

Kindly explaine me as examplewise.

Regards

Prashant

[daniel.dib]

Maximum paths decides how many routes are installed into the RIB/FIB. I think the current default is 4.

If you set it to 1 then only one path can be installed even if you have multiple paths of the same cost.

CEF will handle the load sharing and use a hashing algorithm to decide which flows go over which interface. Normally this is done per destination but per packet can be enabled as well although it is not recommended.

[Sandeep Choudhary]

Hi Prashant,

EIGRP defaults to 4 paths for load balancing but the maximum that can be set is 16

To disable equal cost load balancing, use maximum-path 1 command.

Here is the link of load balancing example.

http://blog.networkfoo.org/2013/08/eigrp-load-balancing.html

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094820.shtml

http://gns3vault.com/EIGRP/eigrp-maximum-path-and-variance.html

Regards

[Joseph W. Doherty]

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Posting

The purpose of the command is to allow you to adjust the number of routes, to the same destination, allowed in the route table.  The command is often used when you want to have more than the router's default number.  For example, say you had 6 T1 routed links between a pair of EIGRP routers.  To distribute traffic across all six, you would set maximum-paths to 6.

EIGRP, by default, does equal cost load balancing, but it can also do unequal cost load balancing.

[daniel.dib]

I'm nitpicking a bit but it's called load sharing. Load balancing is where you actually try to balance the load. CEF does not work like that.

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

daniel.dib wrote:
I'm nitpicking a bit but it's called load sharing. Load balancing is where you actually try to balance the load. CEF does not work like that.

Laugh - well it is nitpicking, but as I'm a nitpicker myself, I won't fault you for that.

One reason I used "load balancing" is that's because that's what the OP used.  I didn't see a need to draw a distinction especially since not everyone agrees there's such a distinction.  For example if you refer to this Cisco tech note, http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094820.shtml, on "Load Balancing", you'll see it explicitly uses load balancing to reference both equal and unequal cost routing for EIGRP.  (Note: this Cisco tech note does say CEF works like that.)

On the other hand, in this Cisco tech note, http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00800945bf.shtml, Cisco uses the term "load sharing", when basically doing the same thing but with BGP.

This distinction Cisco seem to draw between these two tech notes, load balancing is only for egress, but load sharing can also include ingress.

Again, not everyone agrees if there's always a distinction, or what the distinction is.  The question, itself, even arises on these forums, e.g. https://supportforums.cisco.com/thread/2007101.