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Help: br0 brings down ethernet

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  Help: br0 brings down ethernet Alain D D Williams <addw@phcomp.co.uk> - 2020-11-14 15:20 +0100
    Re: Help: br0 brings down ethernet Dan Ritter <dsr@randomstring.org> - 2020-11-14 15:40 +0100

#228649 — Help: br0 brings down ethernet

I'm upgrading my desktop from CentOS-6 to Debian -- CentOS-8 has Gnome 3 that I
can't abide, Debian has Mate.

Most of it works nicely; one problem is starting a network bridge takes down
the ethernet connection.

Can anyone please offer any clues:

/etc/network/interfaces.d/br0 contains:
iface br0 inet static
	bridge_ports enp3s0
	address 10.239.239.254
	broadcast 10.239.239.255
	netmask 255.255.255.0
	# Without this: when a VM starts the rest of the machine loses Internet connectivity - dunno why
	bridge_stp off
	bridge_maxwait 0
	bridge_fd 0

/etc/network/interfaces.d/enp3s0 contains:
auto enp3s0
iface enp3s0 inet static
	address 192.188.145.2
	broadcast 192.188.145.255
	netmask 255.255.255.0
	gateway 192.188.145.1

(It is a wired [utp] ethernet)

(Loopback is also defined somewhere)

Note that br0 is NOT brought up automatically (although I will want that eventually.)

I bring it all up and then:
    ifup br0

And some time later enp3s0 will stop.

'Some time' varies, I have seen 5 minutes and 45 minutes. Without br0 it has
been stable - ie about a day.

It failed just now (after I brought up br0), there was little network activity:
a bit of web browsing; SMTP in/out; idle openvpn; a ping to news.bbc.co.uk

Relevant lines from /var/log/messages:

When I typed: ifup br0

Nov 14 12:30:51 mint kernel: [96153.146266] br0: port 1(enp3s0) entered blocking state
Nov 14 12:30:51 mint kernel: [96153.146269] br0: port 1(enp3s0) entered disabled state
Nov 14 12:30:51 mint kernel: [96153.146396] device enp3s0 entered promiscuous mode
Nov 14 12:30:51 mint kernel: [96153.190042] br0: port 1(enp3s0) entered blocking state
Nov 14 12:30:51 mint kernel: [96153.190046] br0: port 1(enp3s0) entered forwarding state
Nov 14 12:30:51 mint kernel: [96153.190140] IPv6: ADDRCONF(NETDEV_UP): br0: link is not ready
Nov 14 12:30:52 mint kernel: [96154.164444] IPv6: ADDRCONF(NETDEV_CHANGE): br0: link becomes ready

A few minutes after it failed when I typed:

    ifdown br0
    ifdown enp3s0
    ifup   enp3s0

Nov 14 13:19:36 mint kernel: [99078.474136] br0: port 1(enp3s0) entered disabled state
Nov 14 13:19:36 mint kernel: [99078.554460] device enp3s0 left promiscuous mode
Nov 14 13:19:36 mint kernel: [99078.554492] br0: port 1(enp3s0) entered disabled state
Nov 14 13:19:59 mint kernel: [99101.806231] RTL8211E Gigabit Ethernet r8169-300:00: attached PHY driver [RTL8211E Gigabit Ethernet] (mii_bus:phy_addr=r8169-300:00, irq=IGNORE)
Nov 14 13:20:02 mint kernel: [99104.114206] r8169 0000:03:00.0 enp3s0: Link is Up - 1Gbps/Full - flow control off

/var/log/syslog tells me that it failed a few minutes before I noticed:
Nov 14 13:14:24 mint openvpn[3435]: TLS Error: TLS key negotiation failed to occur within 60 seconds (check your network connectivity)
Nov 14 13:14:24 mint openvpn[3435]: TLS Error: TLS handshake failed


Why to I want br0 ?
*******************

The reason that I want a bridge is so that virtual machines (under kvm) can
connect to the host machine and to the Internet. This problem happens even if
VMs are not running.

My machine has:

enp3s0	192.168.145.2 - connected to broadband router

I want:

br0	10.239.239.254

Virtual machines with addresses like 10.239.239.12 that they can see the outside world.


-- 
Alain Williams
Linux/GNU Consultant - Mail systems, Web sites, Networking, Programmer, IT Lecturer.
+44 (0) 787 668 0256  https://www.phcomp.co.uk/
Parliament Hill Computers Ltd. Registration Information: https://www.phcomp.co.uk/Contact.html
#include <std_disclaimer.h>

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#228650

Alain D D Williams wrote: 
> Most of it works nicely; one problem is starting a network bridge takes down
> the ethernet connection.
> 
> Can anyone please offer any clues:
> 
> /etc/network/interfaces.d/br0 contains:
> iface br0 inet static
> 	bridge_ports enp3s0

This tells br0 to eat enp3s0. That's your problem.

> 	address 10.239.239.254
> 	broadcast 10.239.239.255
> 	netmask 255.255.255.0
> 	# Without this: when a VM starts the rest of the machine loses Internet connectivity - dunno why
> 	bridge_stp off
> 	bridge_maxwait 0
> 	bridge_fd 0
> 
> /etc/network/interfaces.d/enp3s0 contains:
> auto enp3s0
> iface enp3s0 inet static
> 	address 192.188.145.2
> 	broadcast 192.188.145.255
> 	netmask 255.255.255.0
> 	gateway 192.188.145.1
> 

Options:

1. keep enp3s0 and br0 separate; turn on routing and route between them.

2. make enp3s0 a blank interface (no IP assignments), keep it as an
assigned port of br0, and make sure br0 has the IP assignment to the
outside world. You can have multiple IPs per NIC.


-dsr-

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