Load balancing in link aggregation

[badalam_nt]

Is it possible to use load balancing per packet inside link aggregation ?

[adamclarkuk_2]

Answer to P.S.

The forum screws up the entry

If you are LB based on src or dst port then that would suggest that one HOST could use multiple links based on port numbers.

Have a play with this cool little command :-

test etherchannel load-balance interface port-channel number {ip | l4port | mac} [source_ip_add | source_mac_add | source_l4_port] [dest_ip_add | dest_mac_add | dest_l4_port] command.

P.S.

Don't forget to rate any posts you have found useful ;-)

[badalam_nt]

Just popped-up a question: how a switch knows about Layer4 TCP ports ???

Is only 6500 series switches that know about L4 ports ? Or any other switch can do this?

PS: Yes, I'm always rating the posts, but normally at the end when I consider to stop the conversations. So it should come soon.

[adamclarkuk_2]

6500/3550/3560/3750/3750-e + others

MLS ( Multi layer switching ) gives these bad boys this ability.

[Correction]

I was talking about L4 in general, not specific the etherchannel, sorry :-s

P.S.

Don't forget to rate any posts you have found useful ;-)

[Jon Marshall]

Adam

According to the link i posted earlier only the 6500/4500 platforms can load-balance on layer 4 information.

Jon

[badalam_nt]

And to finalize the discussion: please could you confirm me black on white that a PC1 to PC2 communication (my example given before) can benefit from the etherchannel?

Some posts above the conclusion was that it cannot benefit at all.

Now I see that actually if using Layer4 ports for configuring the balancing algorithm the PC1 to PC2 end-to-end communication could double its bandwidth compared non-etherchannel situation with 1 link only.

Sorry, I need this confirmation clearly stated for gaining confidence.

[adamclarkuk_2]

All yours Jon ;-), you have done all the hard work on this one

[Jon Marshall]

Adam

Think we both put a bit of effort in :-), and we both got rated for it.

Jon

[Jon Marshall]

Petru

As i said if the switch support L4 load-balancing ie. the 4500 & 6500 then yes you could have multiple conversations among the same 2 PC's using different links in the etherchannel bundle as long as these conversations were on different ports.

If the switch only supports mac/IP then you will always use the same link no matter how many conversations.

Jon

[Jon Marshall]

Petru

If the switch can load-balance on L4 info such as the 6500/4500 then yes you could actually have more than conversation between the same 2 PC's being sent over different links in the etherchannel.

Jon

[Jon Marshall]

Giuseppe

"actually you mean that a detailed forwarding entry is not built but each frame is processed on the fly through the hash algorythm."

Exactly, which means it is not really flow based load-balacing at all ie. per packet load-balancing on a L3 device means that the device makes a forwarding decision based on each packet. This is exactly what a switch does with etherchannel. So to say it is flow based is i think a bit misleading.

The other problem with saying etherchannel is flow based is what constitutes a flow because different switches can use different criteria.

So we get the confusing state where a switch that can only load-balance on mac/IP will always use the same link for the same 2 endpoints but a switch that can load-balance on L4 ports can use multiple links within the etherchannel for the same 2 endpoints.

Jon