[j-nsp] EX4100/EX4400 1GE autoneg issues on SFP+ ports

[Bernhard Schmidt]

Hey,

maybe someone has a quick idea before I pester JTAC for weeks without
success.

We are starting to migrate our campus network to Juniper EX4100/EX4400
series and we have hit a blocker. We've now had several cases where we
could not get a working 1GE fiber connection when the Juniper side was
in a SFP+ slot

First issue with a EX4100-F-12P with an original JNPR 1GE-LX optics in
ge-0/1/0, the other side being an unmanaged media converter. Running
22.4R3.25

Second issue was a EX4400-48F with a third-party 1GE-SR optics in
ge-0/0/36+, the other side being a Huawei S5720 switch. Running
23.4R1.9.

In both cases the behaviour is the same

- JNPR sees link-up, no incoming packets
- the other side sees the link as down, but has a decent Rx power

We know of these 1GE fiber autoneg issues from our Arista core (where,
according to Arista, there is just no 25G chip available on the market
that can do 1GE with auto-neg), so we have to disable 1GE autonegotation
on the other side in the few cases this is happening. But this is
campus, so we don't have control over the other side, and it even
happened with unmanaged converters.

I think it's the autoneg issue because when I add "undo negotiation auto"
on the Huawei side the link comes up there as well, and we can pass
traffic just fine. However, that's not an option in Campus, see above.

Also, moving the link from port 36 (1G/10G) to port 35 (1G only) on the
EX4400-48F fixes the issue as well.

I have tried (on the EX4100-F)

set interfaces ge-0/1/0 ether-options auto-negotiation

and optionally

set interfaces ge-0/1/0 speed auto

according to 

| Autonegotiation is enabled by default, and will autonegotiate the
| speed with the link partner. We recommend that you keep autonegotiation
| enabled for interfaces operating at 100M and 1G. By default,
| autonegotiation is disabled on 10-Gigabit fiber ports.

| If for some reason you have disabled autonegotiation, you can enable it
| by issuing the set interfaces name ether-options auto-negotiate command.

| To disable autonegotiation, issue the delete interfaces name
| ether-options auto-negotiate command.

to no avail.

Does anyone have any idea how I can beat the Juniper side into doing
autoneg on 1GE fiber?

Bernhard