New problem with Network connections and VM

I can almost hear the groans as I post this but after a period of relative stability, on returning to use my VM using the button in my task manager I received an error message Cannot get interface on ‘br0’:No such device.
I checked my NM connections and found I had four. There should have been only three, two ethernet connections and a bridge.
Now I have not touched NM, the only possible network activity I can think of is trying to sort out my APC UPS systems using apcupsd with snmc. Whatever the cause, I had to go back to Malcolm’s guide for setting up my VM and reconfigure all my connections. For this machine I have two wired connections to the network switch rather than one and an usb dongle but Malcolm’s instructions are clear and I was able to get my VM up and running but although I do not have an USB dongle or in fact any USB devices on this machine I find that there is an hidden connection:

alastair@ibmserv2:~> ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 34:40:b5:93:38:d0 brd ff:ff:ff:ff:ff:ff
    altname eno1
    altname enp11s0f0
    inet 192.168.169.134/25 brd 192.168.169.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::9fef:a051:9a5c:190d/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master br0 state UP group default qlen 1000
    link/ether 34:40:b5:93:38:d1 brd ff:ff:ff:ff:ff:ff
    altname eno2
    altname enp11s0f1
4: usb0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 1000
    link/ether 36:40:b5:93:38:d5 brd ff:ff:ff:ff:ff:ff
    altname enp0s26f1u2
8: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 34:40:b5:93:38:d1 brd ff:ff:ff:ff:ff:ff
10: vnet0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br0 state UNKNOWN group default qlen 1000
    link/ether fe:54:00:00:4f:f5 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::fc54:ff:fe00:4ff5/64 scope link 
       valid_lft forever preferred_lft forever
alastair@ibmserv2:~> 

I have no idea where the usb0 came from but I surmise this is an artifact from IBM connected with their original support system for servers. Whatever it is it was this that somehow became involved in my otherwise stable NM settings.
Can anybody explain and more importantly tell me if it is OK to disable this usb connection? For the record it had never been used as I do not have a relevant IBM account.

Investigate the connected USB devices for yourself

usb-devices
inxi -Nna

Assuming IMM, you can generally disable/cofigure via the BIOS as required.

Maybe a good idea to tell us the server model. Others may be able to provide more specific advice about inhibiting the lights-out management port if not required in your situation. (The Linux OS can be configured to ignore it via a udev rule if desired.)

Hi Dean,
Many thanks for the suggested commands which gave me quite a surprise.
The machine is one of a pair of IBM X3400 M3 servers. The IBM machine type is 7379 model W03 and was made in Hungary in 2012!!!

I think I probably have enough information and here are the USB ports:

alastair@ibmserv2:~> usb-devices

T:  Bus=01 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=12  MxCh= 2
D:  Ver= 1.10 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0001 Rev=05.14
S:  Manufacturer=Linux 5.14.21-150500.55.65-default uhci_hcd
S:  Product=UHCI Host Controller
S:  SerialNumber=0000:00:1a.0
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   2 Ivl=255ms

T:  Bus=02 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=12  MxCh= 2
D:  Ver= 1.10 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0001 Rev=05.14
S:  Manufacturer=Linux 5.14.21-150500.55.65-default uhci_hcd
S:  Product=UHCI Host Controller
S:  SerialNumber=0000:00:1a.1
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   2 Ivl=255ms

T:  Bus=02 Lev=01 Prnt=01 Port=01 Cnt=01 Dev#=  2 Spd=12  MxCh= 0
D:  Ver= 2.00 Cls=02(commc) Sub=00 Prot=00 MxPS=64 #Cfgs=  2
P:  Vendor=04b3 ProdID=4010 Rev=02.15
S:  Manufacturer=IBM
S:  Product=RNDIS/CDC ETHER
C:  #Ifs= 2 Cfg#= 1 Atr=c0 MxPwr=100mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=02(commc) Sub=06 Prot=00 Driver=cdc_ether
E:  Ad=82(I) Atr=03(Int.) MxPS=  16 Ivl=32ms
I:  If#= 1 Alt= 1 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=cdc_ether
E:  Ad=01(O) Atr=02(Bulk) MxPS=  64 Ivl=0ms
E:  Ad=81(I) Atr=02(Bulk) MxPS=  64 Ivl=0ms

T:  Bus=03 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=12  MxCh= 2
D:  Ver= 1.10 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0001 Rev=05.14
S:  Manufacturer=Linux 5.14.21-150500.55.65-default uhci_hcd
S:  Product=UHCI Host Controller
S:  SerialNumber=0000:00:1d.0
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   2 Ivl=255ms

T:  Bus=03 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#=  3 Spd=1.5 MxCh= 0
D:  Ver= 1.10 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
P:  Vendor=1061 ProdID=0101 Rev=01.00
S:  Manufacturer=Motorola
S:  Product=USB Keyboard & Mouse
C:  #Ifs= 2 Cfg#= 1 Atr=a0 MxPwr=100mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=03(HID  ) Sub=01 Prot=01 Driver=usbhid
E:  Ad=81(I) Atr=03(Int.) MxPS=   8 Ivl=10ms
I:  If#= 1 Alt= 0 #EPs= 1 Cls=03(HID  ) Sub=01 Prot=02 Driver=usbhid
E:  Ad=82(I) Atr=03(Int.) MxPS=   8 Ivl=10ms

T:  Bus=04 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=12  MxCh= 2
D:  Ver= 1.10 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0001 Rev=05.14
S:  Manufacturer=Linux 5.14.21-150500.55.65-default uhci_hcd
S:  Product=UHCI Host Controller
S:  SerialNumber=0000:00:1d.1
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   2 Ivl=255ms

T:  Bus=05 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=12  MxCh= 2
D:  Ver= 1.10 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0001 Rev=05.14
S:  Manufacturer=Linux 5.14.21-150500.55.65-default uhci_hcd
S:  Product=UHCI Host Controller
S:  SerialNumber=0000:00:1d.2
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   2 Ivl=255ms

T:  Bus=06 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=480 MxCh= 6
D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0002 Rev=05.14
S:  Manufacturer=Linux 5.14.21-150500.55.65-default ehci_hcd
S:  Product=EHCI Host Controller
S:  SerialNumber=0000:00:1a.7
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   4 Ivl=256ms

T:  Bus=07 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=480 MxCh= 6
D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0002 Rev=05.14
S:  Manufacturer=Linux 5.14.21-150500.55.65-default ehci_hcd
S:  Product=EHCI Host Controller
S:  SerialNumber=0000:00:1d.7
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   4 Ivl=256ms
alastair@ibmserv2:~> 

I know of one internal USB socket I did use with a small memory stick for a while for booting when I installed the NVME card because this could not boot but later I removed the USB device as I had partitions on the hard drive I could use for booting. The other six USB connections are all on front or rear panels and one rear socket is used for a mouse/keyboard adaptor.

The second surprise and possible explanation of why my network configuration has been a problem is shown here:-

alastair@ibmserv2:~> inxi -Nna
Network:
  Device-1: Broadcom NetXtreme II BCM5716 Gigabit Ethernet vendor: IBM
    driver: bnx2 v: kernel pcie: gen: 2 speed: 5 GT/s lanes: 4 port: N/A
    bus-ID: 0b:00.0 chip-ID: 14e4:163b class-ID: 0200
  IF: eth0 state: up speed: 1000 Mbps duplex: full mac: 34:40:b5:93:38:d0
  Device-2: Broadcom NetXtreme II BCM5716 Gigabit Ethernet vendor: IBM
    driver: bnx2 v: kernel pcie: gen: 2 speed: 5 GT/s lanes: 4 port: N/A
    bus-ID: 0b:00.1 chip-ID: 14e4:163b class-ID: 0200
  IF: eth1 state: up speed: 1000 Mbps duplex: full mac: 34:40:b5:93:38:d1
  Device-3: IBM RNDIS/CDC ETHER type: USB driver: cdc_ether bus-ID: 2-2:2
    chip-ID: 04b3:4010 class-ID: 0a00
  IF: usb0 state: unknown speed: 9 Mbps duplex: half mac: 36:40:b5:93:38:d5
  IF-ID-1: br0 state: up speed: 1000 Mbps duplex: unknown
    mac: 34:40:b5:93:38:d1

I have no idea how to interpret the usb0 or to which USB port it relates. I will have to check that I did remove the stick but can only do this when cleaning the server as I have to remove components to get to it. I do not think this is relevant.

The clue is in the two Bus=02 lines but how to interpret them is beyond me. Can you shine any light on this please?

It has nothing to do with the memory stick. Here’s a further reference for you

Did you get a CD or manual with your appliance? Did you try disabling the RNDIS/CDC device via the BIOS?

Hi Dean,
Thanks for doing the legwork for this search, I couldn’t make much headway myself when trying to get updates for the BIOS. I might be able to find the CDs but am not sure as there have been many changes and a house move here!

The symptoms are as I suspected but I still do not understand quite how this IMM interface works. All know is that NM does see it and on occasions (as I recall when trying to update the BIOS,) the IMM activity pops up and tries to make a connection but it does not work. I assume because the service has long ceased.

I shall go into the BIOS and see what there is about IMM but it might be better to disable within NM rather than possibly compromising the underlying BIOS. My thoughts uttered in ignorance I confess but I shall go into BIOS and snoop around when I am at the machine.

Many thanks,
Alastair.

Well I’m not sure why the presence of another network interface should concern you. It shouldn’t affect the existing network configuration you have. In any case you can configure Networkmanager to include unmanaged devices so that it ignores them.

Refer ‘KEYFILE SECTION’

man networkmanager.conf

Hi Dean,
I have been into the BIOS and looked at the IMM settings, which I have never done before through ignorance.
The was a switch to disable the internal USB connection which I have done and this has removed the USB so it no longer appears:-

alastair@ibmserv2:~> inxi -Nna
Network:
  Device-1: Broadcom NetXtreme II BCM5716 Gigabit Ethernet vendor: IBM
    driver: bnx2 v: kernel pcie: gen: 2 speed: 5 GT/s lanes: 4 port: N/A
    bus-ID: 0b:00.0 chip-ID: 14e4:163b class-ID: 0200
  IF: eth0 state: up speed: 1000 Mbps duplex: full mac: 34:40:b5:93:38:d0
  Device-2: Broadcom NetXtreme II BCM5716 Gigabit Ethernet vendor: IBM
    driver: bnx2 v: kernel pcie: gen: 2 speed: 5 GT/s lanes: 4 port: N/A
    bus-ID: 0b:00.1 chip-ID: 14e4:163b class-ID: 0200
  IF: eth1 state: up speed: 1000 Mbps duplex: full mac: 34:40:b5:93:38:d1
  IF-ID-1: br0 state: up speed: 1000 Mbps duplex: unknown
    mac: 34:40:b5:93:38:d1
alastair@ibmserv2:~> 

In the BIOS settings I could see there was a burned in MAC address and an IP address set. I cannot understand why this interface shows up as an USB connection and not an ethernet connection since I can only see it when connected to one of the onboard NICs.

The presence of the additional network interface only concerned me when it messed up my working configuration. I have no idea why but now have a better understanding of parts of my machine I didn’t know before. Becoming aware of unmanaged devices and connections helps.

One more question: I first had to look into this when I needed to learn how to use VM and brought into use the second NIC. Before then I do not recall seeing an unheralded USB connection although at about the same time I switched from using wicked to NM. I just wondered if the internal Lan over USB is related to one specific NIC device and only appeared when I started to use the second NIC?

It is not associated with any of the physical ethernet ports at all. It is an internal in-band connection between the host OS and IMM, presented as a LAN over USB interface.

Some more reading for you:

Hi Dean,
Many thanks for the links. I understand a little more now and continue to be impressed by the thought and detail that went into my IBM machines even though I still have much to learn. I still do not know how the NM configurations became corrupted but gladly admit it would have been my own error if only of omission. Finding and disabling the IMM connection in the BIOS was the right answer and for now all is well once more.
Regards,
Alastair.