etherchannel bandwidth

Unanswered Question
Mar 28th, 2007

I'm setting up an etherchannel group to our Lefthand Network SAN. Looking at the design of our 4510R switch and line cards, they are grouped into 6 groups of 8 to the fiber at 1G. Is there a best practice to achieve optimal performance for all servers, workstations attached to the switch? Should I split the conections up on differeny line cards? all on the same? in the same group? Any help would be appriciated.

Thank you.

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m.matteson Wed, 03/28/2007 - 10:25

to my knowledge you can't group multiple Gbps links together for an aggregate of n Gbps. You will get only 1GB throughput and the other links would be standby links. It would be a fail over solution.

Jon Marshall Wed, 03/28/2007 - 13:13

Hi Mike

Which blades are you looking at specifically. Cisco do docs on each blade that shows the port groupings just in case you weren't aware of them. So for example:

the WS-X4418-GB blade

Ports 1 & 2 are uncontended gigabit

Then there are 16 gigabit ports which are oversubscribed and are grouped as follows:

Ports 3, 5, 7, 9

•Ports 4, 6, 8, 10

•Ports 11, 13, 15, 17

•Ports 12, 14, 16, 18

So you need to know how the groupings are done to ensure you are using the throughput to the maximum. Even if you are fully populating the blades you can still ensure that a busy critical server is placed with 2 or 3 less important and less busy servers within the same group.

As far as etherchannels go. I would recommend splitting it across blades for throughput but more importantly redundancy.

Hope that answered some of your question


m.matteson Wed, 03/28/2007 - 13:46

i happen to have WS-X6148-GE-TX module and i would have LOVED to port-channel multiple gig ports together for a greater throughput. but....

The WS-X6548-GE-TX, WS-X6548V-GE-TX, WS-X6148-GE-TX, and WS-X6148V-GE-TX modules have a limitation with EtherChannel. EtherChannel is supported on these modules for all configurations (10, 100, and 1000 Mbps speeds) but be aware of these cases of oversubscription when you configure these modules:

On these modules there is a single 1-Gigabit Ethernet uplink from the port ASIC that supports eight ports. For EtherChannel, the data from all links in a bundle goes to the port ASIC, even though the data is destined for another link. This data consumes bandwidth in the 1-Gigabit Ethernet link. For these modules, the sum total of all data on an EtherChannel cannot exceed 1 Gigabit.

You receive a message on the maximum throughput when you add a port of this module to EtherChannel.

C6500> (enable) set port channel 3/5,4/5 mode on

Adding a WS-X6148-GE-TX port to a channel limits the channel's

bandwidth to a maximum of 1Gig throughput

Port(s) 3/5,4/5 channel mode set to on.

C6500> (enable)

Jon Marshall Wed, 03/28/2007 - 13:52

Hi Michael

Those blades are for the 6500 switch. Do you know if the same limitation applies to the 4500 blades.


m.matteson Wed, 03/28/2007 - 14:22

hey don, i don't know if the limitation is for copper based modules or fiber based.

m.matteson Wed, 03/28/2007 - 14:19

what is the module that you will have the fiber connected too?

show module all command should list the model #

mikehatton Thu, 03/29/2007 - 10:03

I'm using the X4548-GB Line Cards and supervisor engin V. If i use 802.3ad doesnt' that in turn "increase" bandwidth to my equipment? I want to make sure I place the cables in the correct ports to get best preformace out of the switch


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