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New Member

layer-3 port channel

Hi,

I've to put 4 ports in Layer-3 port channel. will all 4 ports be passing the traffice once this port-channel starts functioning?

Thanks...

5 REPLIES
New Member

layer-3 port channel

Traffic will be automatically load-balanced between all 4 ports.

So yes, they all will be passing traffic.

layer-3 port channel

As Ashwin said, all the 4 ports would be load balancing. Just to add, the default load balancing algorithm would be src-dst-ip. It would be a flow based algorithm (i.e a session between one specific source & destination will always use one link till the time the session is not expired).

New Member

layer-3 port channel

ya as ashwin said traffic will be automatically load-balance between all 4 port if any port is going down state then also they distribute all the traffic equal in remaining 3 port as per algorithm.

New Member

layer-3 port channel

Thanks All. How do we change it to do "per-packet" load balancing?

Cisco Employee

layer-3 port channel

Hello Gavin,

How do we change it to do "per-packet" load balancing?

In short, you don't. Cisco switches do not support per-packet load balancing method on EtherChannels. The primary reason is the possibility of frame reordering which is undetectable at Ethernet and IP layer and may cause serious trouble for the communicating applications.

With EtherChannels, you should make an educated guess as to which address fields (source/dest MAC, source/dest IP, source/dest L4 port) in the outbound traffic are the ones that vary the most, and configure your EtherChannel load balancing method to base its decision upon these most varying address fields. The options usually are:

SW-Dist1(config)# port-channel load-balance ?

  dst-ip       Dst IP Addr

  dst-mac      Dst Mac Addr

  src-dst-ip   Src XOR Dst IP Addr

  src-dst-mac  Src XOR Dst Mac Addr

  src-ip       Src IP Addr

  src-mac      Src Mac Addr

Some higher-level switches may also allow you to use L4 port information (this 3560 running IP Base does not).

Best regards,

Peter

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