See what the switch says it is#

You will end up with a table of what every neighbouring device announces about itself: its name, its port, its capabilities. This is how you find out that eth2 goes to the switch port you thought eth3 did, without walking to the rack.

Before you start#

The operator role and a licence.
LLDP enabled on the switch too. It is a two-sided protocol; one side announcing into silence tells you nothing.

Step 1 — Turn it on#

Services → Diagnostics → Neighbours. The panel has one button.

set service lldp interface all

That is what Turn on (all interfaces) stages. To be selective, name interfaces instead:

set service lldp interface eth1
set service lldp interface eth2

Step 2 — Wait thirty seconds#

Neighbours announce every 30 seconds, so an empty table immediately after turning it on is normal. The page says so, and reports the router's own status error if reading the neighbour table failed.

Check it worked#

Services → Diagnostics → Neighbours shows one row per neighbour, with every field the router reports.

bash

show lldp neighbors

What it settles#

Question	The answer is in
Which switch port is this cable in?	The neighbour's port identifier
Is this trunk port actually configured as a trunk?	The neighbour's VLAN announcements, where the switch sends them
Are both members of this bond on the same switch?	Two rows naming the same neighbour — Bond two ports
Is there something on this segment I did not expect?	A row you cannot account for

The ARP and NDP table is on the same page, which is the other half of "what is out there": LLDP tells you about the devices, ARP tells you about the addresses.

Undoing it#

delete service lldp

The panel's Turn off stages that.