Posted on January 21, 2020 10:08 pm
 |  Asked by shuja naqvi
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We are using DCS-7260CX3-64-F as our spine switches. I have configured one of the interfaces as follows
interface Ethernet5/1
description l5a.r1b12.ams7.nee.tmcs_port_2
load-interval 30
speed forced 40gfull
no switchport

sh int eth5/1 transceiver prop
Name : Et5/1
Administrative Speed: 40G
Administrative Duplex: full
Operational Speed: 40G
Operational Duplex: full
Media Type: 40GBASE-SR4
manufacturer: Arista Networks model: QSFP-40G-SR4-AR part number QSFP-40G-SR4-AR rev 02 serial number WX1812200111

The 40G is breaking out into 4 lanes of 10Gs connected to DCS-7020TR-48-R low-performance leaf switches. Config is as below
interface Ethernet49
speed forced 10000full
no switchport

sh int eth49 transceiver pro
Name : Et49
Administrative Speed: 10G
Administrative Duplex: full
Operational Speed: 10G (forced)
Operational Duplex: full (forced)
Media Type: 10GBASE-SR
manufacturer: CISCO-JDSU model: PLRXPL-SC-S43-CS part number PLRXPL-SC-S43-CS rev 1 serial number JUS1737G0UZ
The leaf switch ports are up/up
l7a.r2b12.ams7#sh int status | inc Et49
Et49 connected routed full 10G 10GBASE-SR

But the spine port is not coming up

What additional configuration do I need to bring the ports up on Spine to start configuring the sub-interfaces ?

Answered on January 22, 2020 8:03 am

Hi Shuja,

Since ethernet 5 on the spine is breaking out into 4x10G ports and the neighbor interface et49 is configured as a 10G interface , could you remove the "speed forced 40gfull" command from ethernet5/1 ? This would configure lanes 1-4 of et5 as 10G ports , given that the command "transceiver qsfp default-mode 4x10G" is already present in the running-configuration.


Posted by shuja naqvi
Answered on January 23, 2020 3:14 pm

Thanks for your response. Spine switches are connecting to a patch panel and the patch panel then connects to 7280 R switches. Patch panels host all the break-out links.

I tried your suggestion but it does not work. Previously when spine 1 was connected to the patch panel and I set it to 10g full, the port was down/down and all leaf-pairs had there ports down as well. After by passing the patch panel and connecting spine 1 back to the patch panel with the 10 gig forced on eth5/1 of spine-1 and eth 49 on leaf-5, the ports are up but the rest of the leaf-pairs are down such as leaf6, 7 & 8. Once again if I forced the spine port to 40g full, Eth49 on all leaf ports come up but spine-1 ETH 5/1 stays down.

Posted by Spencer Ryan
Answered on February 8, 2020 8:05 pm

You can not have one end set to 1 x 40G and the other set to 10G even if all 4 ports are going to the same device, the MAC/PHY simply is incapable of this.

You need the QSFP end set to 4 x 10G mode. If ports are not coming up on the other end you have other config issues, but it will never work with one end in 1x40 and the other at 10G

Answered on February 13, 2020 5:21 pm

Hey Shuja,

The optic used on Et5/1 with serial number WX1812200111 is not an Arista certified optic. This looks like a counterfeit one and the behavior cannot be asserted. Arista optics have their serial numbers starting with either 'X' or 'A'.
Can you please try plugging in a known working Arista optic and check if the issue is still seen?

Hope this helps!
Feel free to contact our Technical Support-

Lalitha Prasuna

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