[j-nsp] Force ports with only RX connected to UP

[Phil Mayers]

On 07/02/2010 08:30 AM, John Wilkes wrote:
> Hi.
>
> We have a bunch of fiber taps that we want to aggregate in a Juniper
> EX4200 (24 SFP) before sending it to our network analyzer.
>
> What we thought we would do is connect all the taps to port 0 to X and
> then mirror the traffic from them to port 23.
>
> Problem: We don't get link up when we only connect to RX. It seems the
> switch really really wants to talk to someone on the other end.
>
> We have disabled autoneg, set full duplex 1G, and even turned off flow
> control but the ports are still down. We have also reduced the problem
> to connecting two ports directly.
>
> When the ports are fully connected they come up. Pull just one fiber
> and both ports go down.

Huh.

We do a similar thing  (but not on a Juniper EX switch). It "just works".

Your direct test I would expect to fail; pulling the TX fibre will cause 
the far end to signal fault and bring the entire link down.

That should not happen with the tap; the RX port should "see" link and 
valid autoneg signalling (not "aimed" at it, of course!) and just come up.

Are you sure the taps are working i.e. providing a valid light-level and 
so forth? What's the media & distances/powers?

What kind of tap is it? Passive fibre, OEO?

What does "show int ... extensive" show, with the tap inserted into RX?



>
> We have tried turning off lldp, stp, rstp and mstp globally on the
> switch, as well as setting half duplex.

Are any odd protocols running at the *far* end? Can you turn them off?