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OS: JunOS 19.3

Hello all,

I have an unusual problem.

I have two juniper switches (A) and (B) that are connected on multiple ports

I'm aware that this makes no sense for networking.

This setup is not meant to be run in a networking environment.

No real traffic will ever run through this configuration. It is only used to confirm that the two switches are connected via a certain ports. It is part of a test-setup that has to confirm that an internal switch is correctly connected to a labeled panel.

 |SWITCH A  port x| ----- |PANEL [label foo] | ---- [port y SWITCH B]

Test: If switch (A) port x (mac-address) is connected to port y (mac-address) switch (B) then Switch A is connected to the correct panel port with label 'foo'

Spanning tree is activated on both switches, therefore of course, all but one port is down. Since I have to login to Switch B from Switch A, I can not disable STP or this traffic would loop.

I want to find the mac addresses of all connected ports of switch (B) on switch (A) this would work on switch (A) with show ethernet-switching table, but since the ports are blocked, it doesn't work

I tried to use lldp. but that doesn't work on blocked ports either.

I'm obviously not a juniper expert. Has anybody a (creative) idea, how to accomplish this? TIA

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I'm aware that this makes no sense for networking.

Oh, it might.

Reasonable configurations are:

  • link aggregation
  • dedicated link for separate VLANs or VLAN groups
  • redundant links used with RSTP/MSTP

Since I have to login to Switch B from Switch A, I can not disable STP or this traffic would loop.

If you put both ports in different VLANs (at least on one switch), there's no bridge loop and no need for STP. Alternatively, if you configure a static link aggregation group (LAG) there's no loop, MAC addresses might show up on the logical interface only, but LLDP/CDP should work.

Even if you stick to STP, the spanning tree status (show spanning-tree interface) displays the detected loop which is pretty much all you need to know about the (working) link.

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