[ale] ip address on br0 but not on eth0
Chuck Payne
terrorpup at gmail.com
Thu Feb 2 18:55:03 EST 2023
Narahari,
Device that are with things like bond, teaming, or bridges will never have
an ip, unless you did something set eth0 to get ip automatically, I done
it. The mac address will the same because you are using that device again
for bond, teaming, or bridge. Networking needs a physical device to be
used with the software side for what you are using it, where to send the
network traffic and again what to do with it. Like bridge your virtual
devices traffic to that bridge device, in your case. It gets fun when you
doing teaming and take like 4 x 10 GB nic and make on big pipe of 40GB that
are all active. Or you setting up Bonding so that if you lost a nic, you
are setup up because software understand that if the primary goes down, to
switch traffic over to the secondary. Of course you can have your mind blow
that when you use other network software iptables/ufw and one nic is marked
as a wan and other as a lan, where traffic goes. Networking is fun.
Example
Debian using wicked network setting
auto vmbr0
iface vmbr0 inet static
address 192.168.1.2/24
gateway 192.168.1.1
bridge-ports enp8s0 <-- The physical Device being used.
bridge-stp off
bridge-fd 0
You can use brctl to show what devices are connected, by the way you could
have as many bridge devices as physical nics. I used to work at a company
where we have three bridges so that a virtual host could connect to three
different networks.
bridge name bridge id STP enabled interfaces
br0 8000.e6535d5ccfbf yes enp8s0
vnet0
vnet1
Network Manager assigning, you use nmcli to show, after you nmtui to set,
docker0 is a virtual bridge/switch/dhcpd that will bridge all the container
to physical bridge.
[root at yuureibune ~]# nmcli conn show
NAME UUID TYPE DEVICE
enp3s0f0 e8c8bf3d-4d71-399c-baa2-2308bdecfa2d ethernet enp3s0f0
br-8cc4e4945a6a 987d8faf-fa95-4798-ae1d-3d765ac1f91d bridge
br-8cc4e4945a6a
docker0 25fd5c1d-f7e3-464b-9f75-fca61903e3ef bridge docker0
enp3s0f1 e7c9282a-aee1-4e8f-bdf7-bbe81a97fbd0 ethernet --
enp4s0f0 2daf7843-3147-4753-8225-ddd12f54a0a9 ethernet --
enp4s0f1 e2559e38-2062-4460-865a-ddb11a39964b ethernet --
ip link show
[root at yuureibune ~]# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode
DEFAULT group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp3s0f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP
mode DEFAULT group default qlen 1000
link/ether 44:1e:a1:59:f0:54 brd ff:ff:ff:ff:ff:ff
3: enp3s0f1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state
DOWN mode DEFAULT group default qlen 1000
link/ether 44:1e:a1:59:f0:56 brd ff:ff:ff:ff:ff:ff
4: enp4s0f0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state
DOWN mode DEFAULT group default qlen 1000
link/ether 44:1e:a1:59:e0:e8 brd ff:ff:ff:ff:ff:ff
5: enp4s0f1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state
DOWN mode DEFAULT group default qlen 1000
link/ether 44:1e:a1:59:e0:ea brd ff:ff:ff:ff:ff:ff
6: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue
state DOWN mode DEFAULT group default
link/ether 02:42:51:b6:25:70 brd ff:ff:ff:ff:ff:ff
7: br-8cc4e4945a6a: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc
noqueue state UP mode DEFAULT group default
link/ether 02:42:02:18:8a:c8 brd ff:ff:ff:ff:ff:ff
9: veth006d14f at if8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc
noqueue master br-8cc4e4945a6a state UP mode DEFAULT group default
With both of these, the software side of networking will now send any
traffic to the devices as they are setup as. Bridging a lot easier
now-a-days, use too, you have to have basically write a script to setup
the bridge, turn on bridge control, tree spanning so that you could have
more than one virt go out that bridge, more.
I hope that helps, I am trying to explain from 30,000 Feet.
On Thu, Feb 2, 2023 at 6:18 PM Narahari Lakshminarayana via Ale <ale at ale.org>
wrote:
> Folks:
>
> I am trying to get some networking knowledge. I was setting up a bridge
> and what I see is that I do a br show and I get the ip listed there
> 192.168.0.80
>
> However the eth0 of the VM (not the host) shows no ip address.
>
> The MAC on the br0 has a reference to the eth0 but no ip on the eth0
> entry.
>
> It is so confusing. I thought the eth0 will have ip and not the br0 entry.
>
> In physical connections, the computer will have ip aka the either nic will
> have ip, not the switch or the hub right.
>
> In VM world this br0 comes in the middle and confuses everything.
>
> Isnt br0 in VM world, the equivalent of switch in real world ?
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--
Terror PUP a.k.a
Chuck "PUP" Payne
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