[ale] ip address on br0 but not on eth0

Thu Feb 2 21:59:17 EST 2023

Other really smart people have already responded, but I will say this...
without an authority to issue local IP addresses on your local network, you
will have no IP address issued to your VM, unless it's looking for one.
Switches and stuff do not do this, they only repeat what they are told.

On Thu, Feb 2, 2023 at 6:55 PM Chuck Payne via Ale <ale at ale.org> wrote:

> 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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