Solved: EtherChannels Layer2 Or Layer3?

ifabrizio · ‎02-02-2009

Dear All,

I am planning to configure on my two 6506E with Supervisor32 an Etherchannel, it will be composed by tree ports from the primary supervisor an tree from the redundant one, for each 6506Es.

My dubt is about what type of etherchannel is better for my hardware configuration, Layer3 or Layer2 channels?

Reading the sup32 technical details, I see that the distribution methods for load balancing that are supported on the sup 32 are:

Layer 3 IP: SA;

DA; SA and DA

(Default)

I desume that the better channel type is Layer 3 it is right?

Best regards,

Igor.

Giuseppe Larosa · ‎02-02-2009

Hello Igor,

my undestanding of etherchannel load balancing is that the bundle doesn't need to be L3 to use a L3 based distribution criteria:

it can just use the L3 criteria on IPv4 traffic (ethertype 0x800).

see the following from a C6500 with sup720

sh etherchannel load-balance

EtherChannel Load-Balancing Configuration:

src-dst-ip

mpls label-ip

EtherChannel Load-Balancing Addresses Used Per-Protocol:

Non-IP: Source XOR Destination MAC address

IPv4: Source XOR Destination IP address

IPv6: Source XOR Destination IP address

MPLS: Label or IP

So regardless of the fact if the bundle is a L2 trunk or a L3 link the load balancing work on the traffic type

Of course on a L3 bundle you cannot have non IP traffic over it

We use L2 trunk etherchannels between c6500

Hope to help

Giuseppe

View solution in original post

passioncas · ‎02-02-2009

Hi Igor,

That doesn't make any sense.Depends upon the topology , Layer 2 or Layer 3 ether channels can be configured.By default it is Layer 3 as it is a Layer 3 Switch.That doesn't mean that the Layer 3 ether channel is better than layer2.Even layer 4 load balancing methods can be configured in multilayer Switches.Hope you got it

Mo'ath Al Rawashdeh · ‎02-02-2009

Hi Igor,

passioncas is 100% correct.

Regards.

ifabrizio · ‎02-02-2009

Hi Passioncas,

I read the 6500 Best Praticies, in the paragraph about the Etherchannel's load balancing it says:

"The load distribution algorithm is a global option for both channel control protocols. PAgP and LACP use the

frame distribution algorithm because the IEEE standard does not mandate any particular distribution

algorithms. But, any distribution algorithm ensures that, when frames are received, the algorithm does not

cause the misordering of frames that are part of any given conversation or duplication of frames.

This table illustrates the frame distribution algorithm in detail for each listed platform:

Platform

WS-F6K-PFC3BXL

Load Balancing algorithm

Supervisor Engine32: Layer 3 IP: SA;

DA; SA and DA

You can find the Bestpractices at:

http://www.cisco.com/en/US/products/hw/switches/ps700/products_white_paper09186a00801b49a4.shtml

at pages N 43 and 44.

I agree with you there isn't a best among layer3 and layer2 it dipends by topology.

But reading the Best Practicies seems that the hash used for load balancing with sup32 work at layer 3, what do you think?

Thanks & Bye,

Igor.

Giuseppe Larosa · ‎02-02-2009

Hello Igor,

my undestanding of etherchannel load balancing is that the bundle doesn't need to be L3 to use a L3 based distribution criteria:

it can just use the L3 criteria on IPv4 traffic (ethertype 0x800).

see the following from a C6500 with sup720

sh etherchannel load-balance

EtherChannel Load-Balancing Configuration:

src-dst-ip

mpls label-ip

EtherChannel Load-Balancing Addresses Used Per-Protocol:

Non-IP: Source XOR Destination MAC address

IPv4: Source XOR Destination IP address

IPv6: Source XOR Destination IP address

MPLS: Label or IP

So regardless of the fact if the bundle is a L2 trunk or a L3 link the load balancing work on the traffic type

Of course on a L3 bundle you cannot have non IP traffic over it

We use L2 trunk etherchannels between c6500

Hope to help

Giuseppe

passioncas · ‎02-04-2009

Hi Igor,

Even the Ether Channel is layer 2 or layer 3, the Loadbalancing alg can be layer 2 , layer 3 and layer 4.By default the its layer 3 and the link utilization will be 68% for link 0 and 32 % for Link 1.Better configure Layer4 load balancing so that the link utilizatoi can be made almost 50% on each link

hope to help