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Test port-block constraints on QFX5120 devices
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Description

Problem

Setting ports to 1G speed on the QFX5120-48Y model switches can only be done in blocks of 4.

i.e. in the configuration the port speeds

Configured Port in FPC ConfigRange of Ports Affected
00-3
44-7
88-11
1212-15
1616-19
2020-23
2424-27
2828-31
3232-35
3636-39
4040-43
4444-47

It's been suggested that this limitation does not extend to 10G/25G. So for instance port 0 could be set to 10G and port 1 set to 25G.

We need to understand these limitations in order to properly build the automation to configure ports/port blocks, and also to try to build a safe-check to raise a flag if an invalid combo is used.

Test

What I'd like to do is to use the as-yet unused QFX device in rack E4, cloudsw1-e4-eqiad, to test the valid combinations.

To complete the tests we'd need 2 x 10G DACs and 2 x 25G DACs, or equivalent 10G/25G SFP28 optics/cables (the specific PHY variant doesn't matter). I suspect we probably have kit in stock for the 10G links, not sure if we've any 25G SFPs/DACs in eqiad?

I'd like to connect ports on the switch back-to-back as follows to run some tests:

DeviceLinkPort 1Port 2
cloudsw1-e410G DAC #1024
cloudsw1-e425G DAC #1125
cloudsw1-e410G DAC #2428
cloudsw1-e425G DAC #2832