Linux – Network stop working after adding bridge interface

bridgefedoralinuxlinux-networkingnetworking

I'm using Fedora 25, with kernel 4.11.9, kvm and bridge-utils are installed. I'm following the instructions on http://www.linux-kvm.org/page/Networking#Public_Bridge, to get public bridge. I also have Docker installed on my machine (which creates its own bridges and virtual interfaces).

When I run ip link add br0 type bridge, everything is ok. But after that, when I run ip link set eth0 master br0 my network stop working. The interface eth0 is the interface I use to access the local network and exit to the internet.

What could be going wrong? How can I troubleshoot this?

Best Answer

When you add your ethernet interface to your bridge, you need to move your ipv4 settings from your eth0 to br0 as well. So, first clear eth0 settings and then give your ipv4/6 addresses/gateway/etc to your br0.

Personally I find it convenient to use NetworkManager's GUI (or TUI) to do this task.

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KVM work with bridge network problems

I am giving you my /etc/network/interfaces file where I configured a bridge to use with four VMs on Ubuntu server which also uses KVM (my default lan card is 3rd i.e. 0,1,2,3 so eth2 is used)

auto lo
iface lo inet loopback

# The primary network interface
auto eth2
iface eth2 inet manual

auto br0
iface br0 inet static
        address 192.168.1.17
        netmask 255.255.255.0
        network 192.168.1.0
        broadcast 192.168.100.255
        gateway 192.168.100.100
        # dns-* options are implemented by the resolvconf package, if installed
        dns-nameservers 192.168.103.2
        dns-search mydomain.com
        bridge_ports eth2
        bridge_fd 9
        bridge_hello 2
        bridge_maxage 12
        bridge_stp off

The above is a correct configuration.You might need to check /etc/network/interfaces manual page http://manpages.ubuntu.com/manpages/hardy/man5/interfaces.5.html to understand what the keyword manual in above does.

Post your network interfaces file where you defined bridge then we will be able to help.

I noticed your eth0 and sw0 are having same Mac address. Bridge works on Layer2 that might be source of your problem (some one correct me if I am wrong) and eth0 has IPv6 address where as sw0 has IPv4 address.This is not correct.

Linux bridge responding to arp on wrong interface

http://kb.linuxvirtualserver.org/wiki/Using_arp_announce/arp_ignore_to_disable_ARP should help you, if you ask the bridge to not answer to arp requests.

Best Answer

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KVM work with bridge network problems

Linux bridge responding to arp on wrong interface

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