Problem to setup network-bridge with netplan under Ubuntu 18.04 dedicatet server

I need some help with an server, netplan and a network-bridge..

I want do setup an kvm under my ubuntu 18.04 server, who is reachable from outside. So i need a network-bridge.

So i have simulated the network configuration on a server hosted by my lokal VirtualBox, there i was able to setup an running network configuration with bridge. But i had to enable the promiscuous mode in the virtual box setting.

If i port the setting to my dedicatet hetzner ubuntu server, the internet conection from the server died..

Have somebody an tip for me?

Below the masked netplan config, which is not running (the netplan generate && netplan apply command work successfully).

default working network config:

network: version: 2 renderer: networkd ethernets: enp2s0: addresses: - [IP4] - [IP6] routes: - on-link: true to: 0.0.0.0/0 via: [another IP4] gateway6: fe80::1 nameservers: addresses: - [another IP4] - [another IP4] - [another IP4] - [another IP6] - [another IP6] - [another IP6]

Now my not working 'bridged-config':

network: version: 2 renderer: networkd ethernets: enp2s0: dhcp4: false bridges: br0: interfaces: [enp2s0] addresses: - [IP4] - [IP6] routes: - on-link: true to: 0.0.0.0/0 via: [another IP4] gateway6: fe80::1 nameservers: addresses: - [another IP4] - [another IP4] - [another IP4] - [another IP6] - [another IP6] - [another IP6]

Now i have some outputs after apply the the config:

ifconfig:

br0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 inet [IP4] netmask 255.255.255.255 broadcast 0.0.0.0 inet6 [IP6] prefixlen 64 scopeid 0x0<global> ether 06:54:dd:62:e6:af txqueuelen 1000 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
docker0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 172.17.0.1 netmask 255.255.0.0 broadcast 172.17.255.255 inet6 fe80::42:2bff:febd:df03 prefixlen 64 scopeid 0x20<link> ether 02:42:2b:bd:df:03 txqueuelen 0 (Ethernet) RX packets 17 bytes 760 (760.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 16 bytes 1088 (1.0 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
enp2s0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 ether 44:8a:5b:d4:4f:46 txqueuelen 1000 (Ethernet) RX packets 12143 bytes 1170508 (1.1 MB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 13113 bytes 2062454 (2.0 MB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10<host> loop txqueuelen 1000 (Local Loopback) RX packets 4076 bytes 773559 (773.5 KB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 4076 bytes 773559 (773.5 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
veth5932247: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet6 fe80::289c:28ff:fef6:93f0 prefixlen 64 scopeid 0x20<link> ether 2a:9c:28:f6:93:f0 txqueuelen 0 (Ethernet) RX packets 17 bytes 998 (998.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 20 bytes 1448 (1.4 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
virbr0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 inet 192.168.122.1 netmask 255.255.255.0 broadcast 192.168.122.255 ether 52:54:00:da:13:11 txqueuelen 1000 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

netstat -i

Kernel Interface table
Iface MTU RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg
br0 1500 0 0 0 0 0 0 0 0 BMU
docker0 1500 17 0 0 0 16 0 0 0 BMRU
enp2s0 1500 12143 0 0 0 13113 0 0 0 BMU
lo 65536 4092 0 0 0 4092 0 0 0 LRU
veth5932 1500 17 0 0 0 20 0 0 0 BMRU
virbr0 1500 0 0 0 0 0 0 0 0 BMU

ip r - before apply bridge:

default via [IP4] dev enp2s0 proto static onlink
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1
192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1 linkdown

ip r - with applied bridge:

default via [IP4] dev br0 proto static onlink linkdown
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1 linkdown
192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1 linkdown

ip a

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever
2: enp2s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel master br0 state DOWN group default qlen 1000 link/ether 44:8a:5b:d4:4f:46 brd ff:ff:ff:ff:ff:ff
3: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000 link/ether 52:54:00:da:13:11 brd ff:ff:ff:ff:ff:ff inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0 valid_lft forever preferred_lft forever
4: virbr0-nic: <BROADCAST,MULTICAST> mtu 1500 qdisc fq_codel master virbr0 state DOWN group default qlen 1000 link/ether 52:54:00:da:13:11 brd ff:ff:ff:ff:ff:ff
5: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default link/ether 02:42:51:4d:d0:31 brd ff:ff:ff:ff:ff:ff inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0 valid_lft forever preferred_lft forever inet6 fe80::42:51ff:fe4d:d031/64 scope link valid_lft forever preferred_lft forever
7: vethecd1ee3@if6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP group default link/ether 9a:e0:6b:4c:5b:ae brd ff:ff:ff:ff:ff:ff link-netnsid 0 inet6 fe80::98e0:6bff:fe4c:5bae/64 scope link valid_lft forever preferred_lft forever
14: br0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000 link/ether 06:54:dd:62:e6:af brd ff:ff:ff:ff:ff:ff inet [IP4]]/32 scope global br0 valid_lft forever preferred_lft forever inet6 [IP6]/64 scope global valid_lft forever preferred_lft forever

netplan --debug generate

** (generate:24019): DEBUG: 17:06:17.920: Processing input file /etc/netplan/01-netcfg.yaml..
** (generate:24019): DEBUG: 17:06:17.930: starting new processing pass
** (generate:24019): DEBUG: 17:06:17.930: We have some netdefs, pass them through a final round of validation
** (generate:24019): DEBUG: 17:06:17.930: enp2s0: setting default backend to 1
** (generate:24019): DEBUG: 17:06:17.930: Configuration is valid
** (generate:24019): DEBUG: 17:06:17.930: br0: setting default backend to 1
** (generate:24019): DEBUG: 17:06:17.930: Configuration is valid
** (generate:24019): DEBUG: 17:06:17.930: Generating output files..
** (generate:24019): DEBUG: 17:06:17.930: NetworkManager: definition enp2s0 is not for us (backend 1)
** (generate:24019): DEBUG: 17:06:17.930: NetworkManager: definition br0 is not for us (backend 1)

netplan --debug apply

DEBUG:command generate: running ['/lib/netplan/generate']
DEBUG:netplan generated networkd configuration changed, restarting networkd
DEBUG:no netplan generated NM configuration exists
DEBUG:enp2s0 not found in {}
DEBUG:br0 not found in {}
DEBUG:Merged config:
network: bonds: {} bridges: br0: addresses: - [IP4]]/32 - [IP6]/64 dhcp4: false dhcp6: false gateway6: fe80::1 interfaces: - enp2s0 nameservers: addresses: - [another IP4] - [another IP4] - [another IP4] - [another IP6] - [another IP6] - [another IP6] parameters: forward-delay: 4 stp: true routes: - on-link: true to: 0.0.0.0/0 via: [another IP4] ethernets: enp2s0: dhcp4: false dhcp6: false vlans: {} wifis: {}
DEBUG:Skipping non-physical interface: lo
DEBUG:Skipping composite member enp2s0
DEBUG:Skipping non-physical interface: virbr0
DEBUG:Skipping non-physical interface: virbr0-nic
DEBUG:Skipping non-physical interface: docker0
DEBUG:Skipping non-physical interface: vethecd1ee3
DEBUG:{}
DEBUG:netplan triggering .link rules for lo
DEBUG:netplan triggering .link rules for enp2s0
DEBUG:netplan triggering .link rules for virbr0
DEBUG:netplan triggering .link rules for virbr0-nic
DEBUG:netplan triggering .link rules for docker0
DEBUG:netplan triggering .link rules for vethecd1ee3

Unfortunately this post dont solve my problem:

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