Linux Bridge (vmbr) has no coection to physical NIC

I built myself a new home server and wanted to use Proxmox VE. Its Debian based and I have 3 KVM-machines ruing. Machine 1: "Sophos UTM" has WAN on vmbr0 and DMZ on vmbr1 (192.168.200.254) Machine 2: "OpenMediaVault" (debian based) has LAN on vmbr1 Machine 3: "Xubuntu" just for testing and link into the different networks, currently coected to vmbr1

The Host has 4 GBit-NICs onboard with the Intel 82574L Chipset. Additionally I have a quadport intel NIC installed, just for testing).

eth0 is coected to my home network (192.168.100.0/24) and vmbr0 eth1 is coected to a NAS (192.168.200.200) and vmbr1

The coection between eth0 and vmbr0 is working because the Sophos UTM has a working inteet coection. The machines coected to vmbr1 can also access the web via the Sophos UTM.

My problem is that except one time I caot coect to the NAS on eth1 via vmbr1. The NAS is working and if I plug in directly into the switch between eth1 and the NAS I can access it.

Do you guys have any clue? Is it my fault or is it one of these problems with this particular chipset?

I'd love to get help from you. Feel free to ask further questions.

Here are some data that might be useful for troubleshooting:

ifconfig

eth0      Link encap:Etheet  HWaddr 94:de:80:1d:4d:e2
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:6738 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6997 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:2437530 (2.3 MiB)  TX bytes:4679964 (4.4 MiB)
          Interrupt:17 Memory:fbc00000-fbc20000

eth1      Link encap:Etheet  HWaddr 00:1b:21:37:8a:18
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

eth2      Link encap:Etheet  HWaddr 94:de:80:1d:4d:e3
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:246 errors:0 dropped:0 overruns:0 frame:0
          TX packets:11 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:28707 (28.0 KiB)  TX bytes:932 (932.0 B)
          Interrupt:18 Memory:fbb00000-fbb20000

eth3      Link encap:Etheet  HWaddr 94:de:80:1d:4d:e4
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          Interrupt:16 Memory:fb900000-fb920000

eth4      Link encap:Etheet  HWaddr 00:1b:21:37:8a:19
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

eth5      Link encap:Etheet  HWaddr 94:de:80:1d:4d:e5
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          Interrupt:17 Memory:fb800000-fb820000

eth6      Link encap:Etheet  HWaddr 00:1b:21:37:8a:1c
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

eth7      Link encap:Etheet  HWaddr 00:1b:21:37:8a:1d
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:2864 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2864 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1
          RX bytes:4066008 (3.8 MiB)  TX bytes:4066008 (3.8 MiB)

tap100i0  Link encap:Etheet  HWaddr a2:b0:8a:d3:36:10
          inet6 addr: fe80::a0b0:8aff:fed3:3610/64 Scope:Link
          UP BROADCAST RUNNING PROMISC MULTICAST  MTU:1500  Metric:1
          RX packets:2702 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3119 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:343637 (335.5 KiB)  TX bytes:1652453 (1.5 MiB)

tap100i1  Link encap:Etheet  HWaddr aa:0c:b5:ea:84:54
          inet6 addr: fe80::a80c:b5ff:feea:8454/64 Scope:Link
          UP BROADCAST RUNNING PROMISC MULTICAST  MTU:1500  Metric:1
          RX packets:1777 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1887 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:1223141 (1.1 MiB)  TX bytes:266388 (260.1 KiB)

tap102i0  Link encap:Etheet  HWaddr 32:bf:5a:63:d2:78
          inet6 addr: fe80::30bf:5aff:fe63:d278/64 Scope:Link
          UP BROADCAST RUNNING PROMISC MULTICAST  MTU:1500  Metric:1
          RX packets:1868 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1789 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:264966 (258.7 KiB)  TX bytes:1223985 (1.1 MiB)

vmbr0     Link encap:Etheet  HWaddr 94:de:80:1d:4d:e2
          inet addr:192.168.100.10  Bcast:192.168.100.255  Mask:255.255.255.0
          inet6 addr: fe80::96de:80ff:fe1d:4de2/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:3929 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2349 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:723759 (706.7 KiB)  TX bytes:4196613 (4.0 MiB)

vmbr1     Link encap:Etheet  HWaddr 00:1b:21:37:8a:18
          inet addr:192.168.200.10  Bcast:192.168.200.255  Mask:255.255.255.0
          inet6 addr: fe80::21b:21ff:fe37:8a18/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:64 errors:0 dropped:0 overruns:0 frame:0
          TX packets:11 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:5778 (5.6 KiB)  TX bytes:774 (774.0 B)

vmbr2     Link encap:Etheet  HWaddr 94:de:80:1d:4d:e3
          inet6 addr: fe80::96de:80ff:fe1d:4de3/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:219 errors:0 dropped:0 overruns:0 frame:0
          TX packets:11 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:20499 (20.0 KiB)  TX bytes:870 (870.0 B)

vmbr4     Link encap:Etheet  HWaddr 00:1b:21:37:8a:19
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

/etc/network/interfaces

auto lo
iface lo inet loopback

allow-hotplug eth0

auto eth0
iface eth0 inet manual

allow-hotplug eth1

auto eth1
iface eth1 inet manual

allow-hotplug eth2

iface eth2 inet manual

allow-hotplug eth3

iface eth3 inet manual

allow-hotplug eth4

iface eth4 inet manual

allow-hotplug eth5

iface eth5 inet manual

allow-hotplug eth6

iface eth6 inet manual

allow-hotplug eth7

iface eth7 inet manual

auto vmbr0
iface vmbr0 inet static
        address  192.168.100.10
        netmask  255.255.255.0
        gateway  192.168.100.254
        bridge_ports eth0
        bridge_stp off
        bridge_fd 0


auto vmbr2
iface vmbr2 inet manual
        bridge_ports eth2
        bridge_stp off
        bridge_fd 0

auto vmbr4
iface vmbr4 inet manual
        bridge_ports eth4
        bridge_stp off
        bridge_fd 0

auto vmbr1
iface vmbr1 inet static
        address 192.168.200.10
        netmask 255.255.255.0
        gateway 192.168.200.254
        bridge_ports eth1
        bridge_stp off
        bridge_fd 0

Thanks for your support in advance! :)

-friede