25
votes
Accepted
Bridged interfaces and VLAN tags
Yes: you can set the bridge to be VLAN aware.
The bridge will then handle VLAN IDs attached to frames crossing it, including tagging and untagging them according to configuration, and will send a ...
- 39.5k
18
votes
Accepted
What is virtual bridge with -nic in the end of name
The interface virbr0-nic is not a bridge, but a normal ethernet interface (although a virtual one, created with ip add type veth).
It's there so that the bridge has at least one interface beneath it ...
- 196
18
votes
How to know if a network interface is tap, tun, bridge or physical?
You can use the more-or-less undocumented -d option to ip(8), which tells you the type of certain devices including tun, tap & veth:
e.g.
$ ip -d a
[regular devices]
6: virbr0-nic: <BROADCAST,...
- 301
15
votes
Why assign MAC and IP addresses on Bridge interface
The bridge device listed with your other networking devices does not represent the virtual bridge, it represents a virtual NIC that is connected to the bridge. If you had a physical bridge connected ...
- 159
14
votes
14
votes
Why assign MAC and IP addresses on Bridge interface
Yes, the bridge interface acts as an additional port.
After man 5 systemd.netdev:
A bridge device is a software switch, and each of its slave devices and the bridge itself are ports of the switch.
- 257
14
votes
Accepted
How does iptable work with linux bridge?
Linux' bridge filter framework has available mechanisms where the layer 2 bridge code can do an upcall to iptables (as well as arptables or ip6tables) and have filtering travel from layer 2 (bridged ...
- 39.5k
13
votes
Are bridges like hubs or switches?
A bridge is a network aggregation device, similar in practice to a switch. The bridges implemented in the Linux kernel follow this model. Like any bridge, they forward traffic based on destination MAC ...
- 481k
12
votes
Accepted
Theoretical: TAP interface w/ WIFI parent interface
This Network Engineering SE link Four layer-2 addresses in 802.11 frame header explains quite well the difference between Ethernet and Wifi.
Wifi requires additional MAC addresses for communication: ...
- 39.5k
10
votes
How to allow guest OS to access Internet in qemu?
My second question is - is there an easier way to configure all of this to allow simple internet access to guest os?
You don't (or, at least, shouldn't) need to manually configure anything for simple ...
- 178
10
votes
Accepted
Linux bridge for virtual machines not forwarding IP packets (but is forwarding ARP)
Docker loads the br_netfilter module (to get the sysctl property net.bridge.bridge-nf-call-iptables=1) when it uses iptables. This makes bridged frames (Ethernet, layer 2) subject to iptables ...
- 39.5k
9
votes
Packets not moving through linux ethernet bridge
This is a quite old question, but it might be helpful for others.
Linux bridge might drop packets, if not configured correctly. I had a likewise problem and could solve it with the following ...
- 193
9
votes
Accepted
What is multicast snooping and why does it break UPnP/DLNA?
Multicast may represent a heavy load for switch-routers (not mentioning the security aspect with potential DoS attacks). On a switch (or a Linux bridge), Multicast snooping sits at network layer 2.5 ...
- 18.3k
9
votes
Accepted
Linux VLAN-aware bridges and trunk ports
When using the bridge vlan command, you can add (or delete) a range of VLAN IDs in a single shot. For example:
# bridge vlan add vid 2-4094 dev eth0
will add all available VLANs to the trunk ...
- 39.5k
8
votes
How to know if a network interface is tap, tun, bridge or physical?
This command will do the job:
ip tuntap
Result example:
vnet0: tap
or with details:
ip -details tuntap
Result example:
vnet0: tap
Attached to processes: qemu-system-x86(2225)
- 155
8
votes
Accepted
What exactly does the br_netfilter kernel module control?
First, in order for that module to be of any use to you, you must first be bridging traffic between two or more network interfaces (physical or virtual).
For example, if you want to run QEMU/KVM ...
- 114k
8
votes
Does a linux bridge's port have its own mac address?
Bridges do have their own MAC addresses.
You can change the MAC by doing ip link set <bridge> address <mac>
Once you do that, it keeps the MAC that you set.
Otherwise:
When you create a ...
- 3,621
7
votes
Accepted
Why can't we easily bridge over a wireless NIC
The problem is that wireless frames in the regular mode only have space for three MAC addresses. The details are a bit more complex, but roughly speaking, there's one MAC address for the external ...
- 33.4k
7
votes
Accepted
Adding a physical ethernet interface to kvm qemu bridge
A "physical interface" refers to an actual network device on your computer -- that is, something into which you can plug an ethernet cable, or a wireless network device.
A "virtual ...
- 38.4k
7
votes
Accepted
How can I make Linux generate different MAC addresses for different bridge devices which are on different PCs?
Browsing in Internet I found this bug report on systemd-udev related to Debian 11 bridges: systemd-udev interferes with MAC addresses of interfaces it's not supposed to do
#21185:
ash.in.ffho.net:~# ...
- 39.5k
7
votes
Accepted
What is the net.bridge.bridge-nf-call-iptables kernel parameter?
These parameters determine whether packets crossing a bridge are sent to iptables for processing. Most Kubernetes CNIs rely on iptables, so this is usually necessary for Kubernetes.
The in-kernel ...
- 481k
7
votes
Accepted
why `tcpdump -i any` can't capture unicast traffic in br0 whilst `tcpdump -i br0` can?
According to man tcpdump:
"Note that captures on the 'any' pseudo-interface will not be done in promiscuous mode."
In practice, using the 'any' (pseudo-)interface is not equivalent to ...
- 58k
6
votes
How can I bridge two interfaces with ip/iproute2?
The equivalent of brctl show is bridge link.
You can show the bridge status per device with bridge link show dev eth0 but bridge looks at the network interface and tells you which bridge it belongs to ...
- 101
6
votes
How to create wireless bridge connection with nmcli
It is possible.
If your goal is to create a WiFi Hotspot/Access Point and bridge it to your ethernet connection, you can do that using nmcli.
If your computer is connected to a router via an ethernet ...
6
votes
Transparent Bridge from Existing WiFi to Ethernet?
Ok, I think the main problem here was a communication problem: You were using terms that have a very specific meaning in networking (bridge WLAN to LAN) instead of describing the desired outcome (I ...
- 33.4k
6
votes
Accepted
docker interface tears down wifi internet
It turns out NetworkManager tries to manage and assign an IP address to the veth* network bridge port (I am assuming this is related to the docker0 network bridge).
All these veth* appear in the ...
- 647
6
votes
How can I make Linux generate different MAC addresses for different bridge devices which are on different PCs?
You can tell Debian to clone the MAC address with a bridge_hw directive.
e.g. my /etc/network/interfaces file:
iface enp2s0 inet manual
auto br0
iface br0 inet dhcp
bridge_ports enp2s0
bridge_hw ...
- 49.3k
5
votes
Accepted
Virtual network terminology: is a NATed or routed bridge an oxymoron?
If virbr0 is a bridge, then how can it also function as a NAT?
Well, it doesn't. But the system itself has a port in the bridge, and if there's an IP address set on the bridge, then it can do routing/...
- 148k
5
votes
Accepted
How to set up bridged network with virtual machine and host with KVM (Virt-Manager)?
I've always found that the easiest way to do this, especially if you want the VMs to be just another host on the LAN, is to configure the host machine so that its configured interface(s) are bridges ...
- 84k
5
votes
Accepted
Simulation of packet loss on bridged interface using netem
The reason for this behaviour is described in the tc-netem(8) (bold mine):
delay
adds the chosen delay to the packets outgoing to chosen network
interface.
or
loss random
adds an ...
- 39.5k
Only top scored, non community-wiki answers of a minimum length are eligible