Wierd outputs on switches for same etherchannel

chandra_rc16 · ‎02-03-2014

Hi all,

Here is my topology:

I configure LACP channel b/w Switch1 & switch3. The output on the SW3 for "show etherchannel / show etherchannel port-channel" is fine

but it is in appropriate on Sw1. Can someone please let me know where i'm doing wrong or is this a PT bug?

show etherchannel on Sw1:

Switch1#show etherchannel

Channel-group listing:

----------------------

Group: 1

----------

Group state = L2 // Acutally here the output show the protocol type and ports in it also

Switch1#

----------------------------------------------------------------------------------------

Switch1#show etherchannel port-channel

Channel-group listing:

----------------------

Group: 1

----------

Port-channels in the group:

---------------------------

Port-channel: Po1 (Primary Aggregator)

------------

Age of the Port-channel = 00d:00h:17m:33s

Logical slot/port = 2/1 Number of ports = 2

GC = 0x00000000 HotStandBy port = null

Port state = Port-channel

Protocol = LACP

Port Security = Disabled

Ports in the Port-channel:

Index Load Port EC state No of bits

------+------+------+------------------+-----------

0 00 Fa0/4 0

0 00 Fa0/3 0

Time since last port bundled: 00d:00h:17m:33s Fa0/3

Switch1#

Here the EC state is not shown. I tried configuring it as active and passive but the output doesn't change.

Whereas the same command when issued on SW3 shows the correct output.

Switch3#show etherchannel

Channel-group listing:

----------------------

Group: 1

----------

Group state = L2

Ports: 2 Maxports = 16

Port-channels: 1 Max Port-channels = 16

Protocol: LACP //These 3 lines are missing on SW1 output

Switch3#

-----------------------------------------------------------------

Switch3#show etherchannel port-channel

Channel-group listing:

----------------------

Group: 1

----------

Port-channels in the group:

---------------------------

Port-channel: Po1 (Primary Aggregator)

------------

Age of the Port-channel = 00d:00h:53m:16s

Logical slot/port = 2/1 Number of ports = 2

GC = 0x00000000 HotStandBy port = null

Port state = Port-channel

Protocol = LACP

Port Security = Disabled

Ports in the Port-channel:

Index Load Port EC state No of bits

------+------+------+------------------+-----------

0 00 Fa0/4 Active 0

0 00 Fa0/3 Active 0

Time since last port bundled: 00d:00h:20m:06s Fa0/3

Here the EC state is show correct but not on SW1.

Please put your inputs.

Thanks a lot in advance.

Regards,

Chandu

Regards, Chandu

sbhadrav@cisco.com · ‎05-03-2018

sh etherchannel summary" should show you the links in the etherchannel.

Not sure what you mean about using two links simultaneously. For any single flow only one of the links can be used but if there are multiple flows at the same time they can be spread across the physical links in the etherchannel.

How a flow is defined is dependant on what the switch supports. At its most basic it would be src and dst mac address but you can also have src and dst IPs and port numbers. The configuration guides for the switch model will give you the options.
Etherchannel is treated as one logical link for STP, so if STP blocks the Etherchannel port, all Etherchannel member ports will be blocked.

Etherchannel uses can different criteria (also platform dependent) for how it "hashes" traffic across the links. If only src MAC was being used, flows with the same src MAC will use the same Etherchannel member link. Flows with different src MACs may, or may not, use different member links.

A poor combination of the Etherchannel hashing algorithm will result in all or most traffic using just one member link.

Etherchannel doesn't react to member link usage, or split a flow across links.