Verifying etherchannel status and load-balancing statistics

[SJ K]

Hi all,

I have configured a L2 etherchannel between 2 switches (Cisco 3560-24PS-S) by using the following commands

On the 1st switch, i issue
1) conf t
2) int range fa0/23-24
3) channel-group 1 mode on;

Immediately, the 2 lines went up and the port-channel got created and up.
*This was done on only 1 side of the switch but show etherchannel summary show the PO1 (SU) — Layer2 and in use.

Subsequently, i went to setup the same on the 2nd switch. Connecting a host on each side of the 1st and 2nd switch and pinging each other works.

Q1) However, how do I really verify that the port-channel connectivity between the 2 switches are really working (given that it turn ups even only when 1 side of the portchannel/switch is configured).  (any part of the show etherchannel commands i can use to verify the etherchannel connectivity between the 2 switches are really working) ?

Q2) I have configure src-dst mac load-balancing, but other then using “test etherchannel load-balance”, is there anyway way to see the traffic distribution between the 2 interface/lines on the switch ?

I do a show int fa0/23; and show int fa0/24, trying to a get baseline of the current traffic on both interfaces before sending some packets out, but the output packets on both interfaces jumps all the time before i even actually send the actual traffic out.

How do i verify that both links are actually “used” ?

Q3) The same goes for a L3 port-channel -> how do i really verify the different traffic did really flow through different links (other then using "test etherchannel load-balance"  ?) and i cant monitor the individual interfaces, their packets are always jumping.

Regards,
Noob

[Reza Sharifi · Accepted solution]

Hi,

Q1) However, how do I really verify that the port-channel connectivity between the 2 switches are really working (given that it turn ups even only when 1 side of the portchannel/switch is configured).  (any part of the show etherchannel commands i can use to verify the etherchannel connectivity between the 2 switches are really working) ?

"sh etherchannel xx detail" will give you a lot of good info regarding the portchannel, physical ports, mode, etc..

Q2) I have configure src-dst mac load-balancing, but other then using “test etherchannel load-balance”, is there anyway way to see the traffic distribution between the 2 interface/lines on the switch ?

As far as I know that is the only command.

How do i verify that both links are actually “used” ?

Connect 2 PCs to the switch and send traffic to a destination and use "test etherchannel load-balance” command to see what device (PC) is using which link.  Each PC should use a different physical link since the each MAC address is unique.

Same for layer-3 interfaces.

HTH

[SJ K]

Hi Reza,

Thanks for your reply and sorry for reverting late.

Please see below setup (*I have only done/setup the port-channel interface on S1)

S1(config)#int range fa0/23-24

S1(config-if-range)#switchport access vlan 9

S1(config-if-range)#channel-group 1 mode on
S1#show etherchannel detail
                Channel-group listing:
                ----------------------

Group: 1
----------
Group state = L2
Ports: 2   Maxports = 8
Port-channels: 1 Max Port-channels = 1
Protocol:    -
Minimum Links: 0
                Ports in the group:
                -------------------
Port: Fa0/23
------------

Port state    = Up Mstr In-Bndl
Channel group = 1           Mode = On              Gcchange = -
Port-channel  = Po1         GC   =   -             Pseudo port-channel = Po1
Port index    = 0           Load = 0x00            Protocol =    -

Age of the port in the current state: 0d:00h:01m:43s

Port: Fa0/24
------------

Port state    = Up Mstr In-Bndl
Channel group = 1           Mode = On              Gcchange = -
Port-channel  = Po1         GC   =   -             Pseudo port-channel = Po1
Port index    = 0           Load = 0x00            Protocol =    -

Age of the port in the current state: 0d:00h:01m:45s

                Port-channels in the group:
                ---------------------------

Port-channel: Po1
------------

Age of the Port-channel   = 0d:00h:01m:45s
Logical slot/port   = 2/1          Number of ports = 2
GC                  = 0x00000000      HotStandBy port = null
Port state          = Port-channel Ag-Inuse
Protocol            =    -
Port security       = Disabled

Ports in the Port-channel:

Index   Load   Port     EC state        No of bits
------+------+------+------------------+-----------
  0     00     Fa0/23   On                 0
  0     00     Fa0/24   On                 0

Time since last port bundled:    0d:00h:01m:45s    Fa0/24

I am not really sure which part in the etherchannel detail that indicate the port-channel is working fine or not.

It seems like the port-channel is fine, but in fact only 1 side of the etherchannel is setup.

Is there anywhere i should look at ?

Regards,
Noob

[Reza Sharifi · Accepted solution]

Hi Noob,

When you issue "sh etherchannel summary" and the Portchannel is in "SU" this means the Portchannel is configured as layer-2 (S) and U stands for "in-use".  So in this case the Portchannel is configured correctly and the physical ports are bundled. The way you can test it is by running a continues ping to a destination from a PC and disconnecting one link at a time.

If this works your Portchannel is operating correctly.

HTH

[SJ K]

Hi Reza,

Thanks for your prompt reply!

Yeap. Initially i thought of using the "SU" as a status to verify if the port-channel is ok - but was kinda surprise when i only setup 1 side of the port-channel on 1 switch and it still turn up as "SU".

Guess the only better way is the take out the cable and test yea ?

===

Back to the earlier question 2

Connect 2 PCs to the switch and send traffic to a destination and use "test etherchannel load-balance” command to see what device (PC) is using which link.  Each PC should use a different physical link since the each MAC address is unique.

q2)  i am thinking along the line that  "test etherchannel load-balance"  will work even if there are no PCs connected (it is just use to see which path the traffic will take).

How about really verifying that the traffic did "took" the path indicated by " test etherchannel load-balance"  ?

Is there no debug or other statistics command we can use to see ? ( i am on cisco 3560 ).

Hope to hear from you soon!

Regards,
Noob

[Reza Sharifi · Accepted solution]

Hi Noob,

I don't know of any other command on small switches besides the test command (sample here).

But as I said before if you use 2 PCs you should be able to see 2 different physical ports in the path if this command really works. :-)

I think Cisco has completely removed this command in later versions of IOX XE, which runs on the 3850 series, because I am not able to find it.

test etherchannel load-balance interface port-channel x ip x.x.x.x x.x.x.x”

I only see
test interfaces port-channel xx
Maybe they changed it to something else. Not sure.

[SJ K]

Hi Reza,

Duly noted! Thanks for your advices!

Regards,

Noob

[Bita]

hi,

 i have question a bout etherchand, can you help me?

[Joseph W. Doherty]

"Each PC should use a different physical link since the each MAC address is unique."

BTW, keep in mind, PC MAC scan hash to the same link. In theory (although unlikely), even if you had 100 PCs, all could hash to the same link.

[BilalButt62333]

I also have 2 switches L2 2960  in channel-group 1  and up to fast 0/1-9   as we know max is up to 8 ports so how can I add 0/9 port in hot-standby port because when i   

"show EtherChannel port-channel"  hot-standby port=0 why is it?