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I have 2 arista 100gb switches (7060cx) and an arista 7280sr2k router. i have breakout cables that come from 100g ports on the 7060 switches that go to ports 33-48 on the arista 7280sr2k.  i am unable to get the port channels to come up.  i have tried different port configs….100gb forced on the 7060s for the ports and on the 7280sr2k, 25 gb forced on each port. ports 25-48 are 25gb ports on the 7280 by default.   The cables that i am using are from fs.com: Q4s28pc01 (100g qsfp28 dac 1meter).  Can anyone assist me with this issue?

Posted by Aniket Bhowmick
Answered on January 6, 2021 6:17 am

Hi Maurice,

Thank you for posting your query.

I believe the concern you are having is related to the physical links itself not coming up between 7060 and 7280, rather than the logical port- port-channel (which will come up only after the physical links are up). Is that correct ?

From the problem statement as following: "i have tried different port configs….100gb forced on the 7060s for the ports and on the 7280sr2k, 25 gb forced on each port"

^ It seems you are trying to configure the speed 100G on the 7060 and on the opposite side (7280) you are configuring 25G. Is that correct ?

If yes, then it is expected the physical link will not come up as the speed needs to be same on both side.

Can you please tell me the interface number on the 7060CX device which you are connecting to the 7280 ?

On the 7060cx, have you tried configuring the speed 25G ? If not can you please try using the command "speed forced 25gfull" on both 7060cx ?

Please use the following command- "sh interfaces hardware default" to see which speed and duplexes are supported on a given interface on the switch, along with other details as well. (The command may vary based on the EOS version you are using, let us know if it doesn't work and also the EOS version you are using).

Sample output of the command:

up101...01:10:31(config-if-Et11/1)#sh interfaces hardware default
Model: DCS-7060CX-32S
Type: Not Present
Speed/Duplex: 1G/full,10G/full,25G/full,40G/full,50G/full,100G/full
Flowcontrol: rx-(off,on),tx-(off,on)
Autoneg CL28: 1G/full,10G/full
Autoneg CL73:
IEEE: 40G/full,100G/full
Consortium: 25G/full,50G/full
Error Correction:
Reed-Solomon: 100G
Fire-code: 25G,50G

^ You can use this command to understand what speed is supported on the interface. Make sure to have same speed on both end of the link.

Let us know if there is any further query.



Posted by Schaden Schaden
Answered on January 11, 2021 4:26 am

A port channel is a communication link between two switches supported by  but port channels are not formed when the interface on each switch is passive.  avoided by performing different hash calculations on each switch routing the paths.

Posted by Roberto
Answered on January 14, 2021 9:46 pm

Answer above is correct, the physical port you assigned to the port-channel must be connected.  Let's start with that by determining if the ports are up.  Can you share the following outputs:
show port-channel <#>
show interfaces status

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