USR-ES1 with W5500 does not connect to Fritzbox LAN port

[DerFranki]

Description

If you connect a USR directly to one of the 5 LAN ports on a Fritzbox 7590AX, there is no ethernet connection and both USR-ES1 LEDs flash in turn very briefly every second.
But: a connection is established when a switch or hub is used in between.

The following has been tested:
Short LAN cable: no connection
Long LAN cable: no connection
Cross-over patch cable: no LEDs and no connection at all
Fritzbox LAN port switched to 1Gb or 100M: no connection
Fritzbox EEE (Energy Efficient Ethernet) on or off: no connection
DHCP on or off: no connection
Different USB-C power source: no connection

However:
1 Gbit switch: connection established, ping successful
10 Mbit hub: connection established, ping successful

Is there another relevant setting on the USR-ES1?

Actual behavior

USR-ES1 does not connect to Fritzbox 7590AX

Expected behavior

connection should be established

ebusd version

current source from git

ebusd arguments

%

Operating system

Debian 12 (Bookworm) / Ubuntu 22-23 / Raspberry Pi OS 12 (including lite)

CPU architecture

arm64

Dockerized

None

Hardware interface

Adapter Shield v5/C6/Stick via Ethernet

Related integration

No response

Logs

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