[c-nsp] 3750 Etherchannel loadbalnace

[Arie Vayner]

Chintan,

The switches use a hash function. This means that if you have only 2 MACs,
there is a 50:50 chance that only one link would be used...
If the number of MACs is higher, the chances get better.

On thing you could do is to split the traffic on the MPLS speaker's level by
breaking the etherchannel, and running 2 VLANs end to end (each on a single
link). This would allow the MPLS hosts to make the load sharing decision...

Arie

On Sat, Nov 1, 2008 at 3:46 PM, Chintan Shah <
networking.stuff at googlemail.com> wrote:

> Hi,
>
> I have 3750 aggregation switches as aggregation layer to connect 2  access
> router to Core router. 3750 runs e etherchannel from  to Core with 2 1 gig
> link
>
> I have src-mac based loadbalanced method used in 3750 and what I see
> that 3750 use only one link part of ethrchannel so during test when i have
> total traffic comming more than 1gig , i see drops....
>
> Here are details :
>
>
> Mac address : 000d.edac.8900 – Access Router 1
>
> 0006.d61b3c1a - Access Router r2
>
> 0015.c75d.d42c- Core router
>
> sw1.LAB-3750G#show etherchannel summary | beg Group
> Group  Port-channel  Protocol    Ports
>
> ------+-------------+-----------+-----------------------------------------------
> 1      Po1(SU)          -        Gi2/0/1(P)  Gi2/0/4(P)
>
> sw1.LAB-3750G#
>
>
> sw1.LAB-3750G#test etherchannel load-balance interface port-channel 1 mac
> 000d.edac.8900  0015.c75d.d42c
>
> Would select Gi2/0/1 of Po1
>
>
> sw1.LAB-3750G# test etherchannel load-balance interface port-channel 1 mac
> 0006.d61b.3c1a  0015.c75d.d42c
>
> Would select Gi2/0/1 of Po1
>
> As per above test, I see that 3750 select Gi2/0/1 for two source
> mac-address
> and that's reason i have only one link utilized..
>
> Does some body knows the algorithm used by  3750 for above two source-mac
> address and how did it select always gi2/0/1 not other link for 2nd stream
> of traffic ??
>
> Unforutnately I can't do src-dst-ip based loadbalnace becuase incomming
> traffic is MPLS labelled and existing 3750 doens't have capbility to
> understand MPLS so it takes as non-ip traffic..
>
>
> Thanks in advance,
> Chintan
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