I'm trying to fix an issue on Ampere-based systems such as those with
Altra and AmpereOne CPUs.
When running a desktop such as GNOME in Ubuntu 25.10 there's a pop-up
message every few minutes saying that it failed to configure the network
interface. That's happening because there's an internal USB connection
between the host and BMC that's configured on the BMC side as an
ethernet interface with either a 169.254 or 192.168 (depending on
whether the BMC is running MegaRAC or OpenBMC etc.) static IP address,
and by default NetworkManager tries to get an address via DHCP.
NetworkManager logs the following on my AmpereOne system:
policy: auto-activating connection 'Wired connection 2'
(1b2182a2-3794-3d00-91fd-c13dcd4ca259)
device (enx02ce133e39f7): Activation: starting connection 'Wired
connection 2' (1b2182a2-3794-3d00-91fd-c13dcd4ca259)
device (enx02ce133e39f7): state change: disconnected -> prepare (reason
'none', managed-type: 'full')
device (enx02ce133e39f7): state change: prepare -> config (reason
'none', managed-type: 'full')
device (enx02ce133e39f7): state change: config -> ip-config (reason
'none', managed-type: 'full')
dhcp4 (enx02ce133e39f7): activation: beginning transaction (timeout in
45 seconds)
device (enx02ce133e39f7): state change: ip-config -> failed (reason
'ip-config-unavailable', managed-type: 'full')
device (enx02ce133e39f7): Activation: failed for connection 'Wired
connection 2'
device (enx02ce133e39f7): state change: failed -> disconnected (reason
'none', managed-type: 'full')
dhcp4 (enx02ce133e39f7): canceled DHCP transaction
dhcp4 (enx02ce133e39f7): activation: beginning transaction (timeout in
45 seconds)
dhcp4 (enx02ce133e39f7): state changed no lease
The BMC on this system is running AMI MegaRAC and the USB interface on
the host is:
Bus 001 Device 007: ID 046b:ffb0 American Megatrends, Inc. Virtual Ethernet.
I initially submitted a PR against NetworkManager to set the interface
link-local only and rename it to 'bmc', but I was informed that it
wasn't the correct place for it.
"This rule should be shipped with udev, not with NetworkManager, for two
reasons:
NM is not in the business of renaming interfaces
if the rule is in udev (with ID_NET_AUTO_LINK_LOCAL_ONLY instead of
NM_AUTO_DEFAULT_LINK_LOCAL_ONLY), the link local addressing will work
also with other networking daemon such as systemd-networkd."
It looks like systemd might be the place to put the rules since it
appears to have files to deal with similar situations. For example,
hwdb.d/82-net-auto-link-local.hwdb which I've tried modifying with:
# BMC USB-to-USB links for ASRock Rack and OpenBMC
usb:v26CEp00A0*
usb:v0525pA4A2*
usb:v046bpffb0*
ID_NET_AUTO_LINK_LOCAL_ONLY=1
That didn't work, so now I'm looking at network/73-usb-net-by-mac.link
but from the systemd.link man page I'm not seeing a way to specify a USB
vendor/product.
I was wondering if somebody might be able to help me with where and what
to add?
--
Rebecca Cran
