CRS-1 Load balancing issue

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Mar 1st, 2011
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Dear all,

I am using a simple load balacing based on static routing, running V 3.8.4.

Although checking route and cef details confirms load balancing is as it should be...load on interfaces is very much apart for outpout traffic (input looks fiine).

load interval and configuraion on each interface is exactely the same, no bundling used.

Any thoughts ?



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cisco_lad2004 Tue, 03/01/2011 - 06:20
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Many thanks Naidu,

I am actually not using bundles, its a plain static route over 2 links / ports.


Bryan Garland Wed, 03/02/2011 - 06:48
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The load balancing algorithm used in CRS by default is based on L3, 3 tuple, hash.  So if you don't have enough different l3 source/destination addresses you won't see as even distribution.  Normally this is just fine.  But depending on the traffic flows you have you may need to go to L4, 7 tuple, algorithm.  This will then look deeper into the packets and use the L4 ports along with source and destinations addresses to balance out the flows.

To change this it's global config command "cef load-balancing fields l3/l4". 

This will change the hashing algorithm used on the linecards for load balancing. 



cisco_lad2004 Wed, 03/02/2011 - 06:56
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Many thanks Bryan,

I have also evaluated going for L4 load balancing instead of current default. But this did not make much sense when I noticed I have 4 uplinks load balancing nicely. Whereas access facing links are about 40% out in terms of load balancing...

I am beginning to suspect a cosmetic bug which should be confirmed by getting readings from Customer own devices.

Many thanks again !


ColdDayInHell Mon, 02/25/2013 - 02:25
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Did you managed to find the root cause for this problem , i seem to have the same symtopms , is it a SW bug ?


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