Winbox does not find CRS behind CSS610

Hi,

could anybody give me a hint, please, why winbox does not find a CRS router with routerOS behind a CSS610 (SwOSlite 2.20)?
I can connect directly to the IP of the CRS, my client and the CRS are both in VLAN 1.

client -VLAN1- CRS =trunk= CRS =trunk= CSS610 -VLAN1- CRS

all CRS are detected but the one behind the CSS.
all CRS run RouterOS 7.19.3

any ideas?

best

Gerold

As you mention VLAN 1 explicitely…it is not recommended to use this ID.

Can you share your config?

well, VLAN1 came from history …

meanwhile I gave up, redesigned the network, so the CSS ist the last in chain.
I cannot reproduce the setup identically as the missed CRS was fiber-linked from CSS and both fiber ports of the CSS610 are in use now.
The only thing I could try is a copper-connected CRS

today I performed a test with the same CRS from the original post, in principle the same setup, except that I used a copper connection, not fiber.
Everything works as expected, dicovery works.

How does the router detection from winbox work?
Which packets can get lost on a fiber connection that pass on copper?