Private network bridge is always down

S

SilentPantz

New Member
Oct 18, 2021
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Hello, I am attempting to create a private network for my vms to communicate, which will be on a bridge named vmbr1. I want only one single vm to have access to internet through the default bridge, vmbr0, along with access to vmbr1 to communicate and forward requests to the other vms. I'm having issues configuring these interfaces. I have attempted to follow several guides but I still seem to be missing something. One guide I've mainly been following is this: https://blog.jenningsga.com/private-network-with-proxmox/. I successfully installed and started dnsmasq as instructed in the guide, however I connot get the bridge vmbr1 to go up.

Here is my config so far:
proxmox_network.PNG
[host] /etc/network/interfaces
Code: 
auto lo
iface lo inet loopback

iface enp5s0f0 inet manual

iface enp5s0f1 inet manual

auto vmbr0
iface vmbr0 inet static
        address 192.168.1.105
        netmask 255.255.255.0
        gateway 192.168.1.1
        bridge-ports enp5s0f0
        bridge-stp off
        bridge-fd 0

auto vmbr1
iface vmbr1 inet static
        address 10.10.10.1
        netmask 255.255.255.0
        bridge-ports none
        bridge-stp off
        bridge-fd 0
        post-up   iptables -t nat -A POSTROUTING -s '10.10.10.0/24' -o vmbr0 -j MASQUERADE
        post-down iptables -t nat -D POSTROUTING -s '10.10.10.0/24' -o vmbr0 -j MASQUERADE

[host] ip a
Code: 
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: enp5s0f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master vmbr0 state UP group default qlen 1000
    link/ether 00:30:48:35:3d:64 brd ff:ff:ff:ff:ff:ff
3: enp5s0f1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 00:30:48:35:3d:65 brd ff:ff:ff:ff:ff:ff
4: vmbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 00:30:48:35:3d:64 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.105/24 scope global vmbr0
       valid_lft forever preferred_lft forever
    inet6 fe80::230:48ff:fe35:3d64/64 scope link
       valid_lft forever preferred_lft forever
5: vmbr1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
    link/ether d6:95:21:c4:44:76 brd ff:ff:ff:ff:ff:ff
    inet 10.10.10.1/24 scope global vmbr1
       valid_lft forever preferred_lft forever

My issue is that vmbr1 is down and I'm never able to get the proxy vm to use interface ens19. Even when setting a static IP for this interface in /etc/network/interfaces, the ens19 interface remains down.
[proxy vm] ip a
Code: 
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: ens18: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 66:bb:81:a9:e7:56 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.126/24 brd 192.168.1.255 scope global dynamic ens18
       valid_lft 86171sec preferred_lft 86171sec
    inet6 fe80::64bb:81ff:fea9:e756/64 scope link
       valid_lft forever preferred_lft forever
3: ens19: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
[proxy vm]cat /etc/network/interfaces
Code: 
auto lo
iface lo inet loopback

auto ens18
iface ens18 inet static
     address 192.168.1.105
     netmask 255.255.255.0
     gateway 192.168.1.1

auto ens19
iface ens19 inet static
     address 10.10.10.2
     netmask 255.255.255.0
     gateway 10.10.10.1

And just for good measure, here is my dnsmasq config:
Code: 
interface=ens19
dhcp-range=ens19,10.10.10.3,10.10.10.100,12h
 
Last edited:
you can also try to add a dummy interface:

Code: 
auto dummy0
iface dummy0 inet manual
        link-type dummy

auto vmbr1
iface vmbr1 inet static
        address 10.10.10.1
        netmask 255.255.255.0
        bridge-ports dummy0
        bridge-stp off
        bridge-fd 0
        post-up   iptables -t nat -A POSTROUTING -s '10.10.10.0/24' -o vmbr0 -j MASQUERADE
        post-down iptables -t nat -D POSTROUTING -s '10.10.10.0/24' -o vmbr0 -j MASQUERADE
 
spirit said:
you can also try to add a dummy interface:

Code: 
auto dummy0
iface dummy0 inet manual
        link-type dummy

auto vmbr1
iface vmbr1 inet static
        address 10.10.10.1
        netmask 255.255.255.0
        bridge-ports dummy0
        bridge-stp off
        bridge-fd 0
        post-up   iptables -t nat -A POSTROUTING -s '10.10.10.0/24' -o vmbr0 -j MASQUERADE
        post-down iptables -t nat -D POSTROUTING -s '10.10.10.0/24' -o vmbr0 -j MASQUERADE
Click to expand...

Here is the result of the dummy interface:

Code: 
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: enp5s0f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master vmbr0 state UP group default qlen 1000
    link/ether 00:30:48:35:3d:64 brd ff:ff:ff:ff:ff:ff
3: enp5s0f1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 00:30:48:35:3d:65 brd ff:ff:ff:ff:ff:ff
14: vmbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 00:30:48:35:3d:64 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.105/24 scope global vmbr0
       valid_lft forever preferred_lft forever
    inet6 fe80::230:48ff:fe35:3d64/64 scope link
       valid_lft forever preferred_lft forever
15: vmbr1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
    link/ether d6:95:21:c4:44:76 brd ff:ff:ff:ff:ff:ff
    inet 10.10.10.1/24 scope global vmbr1
       valid_lft forever preferred_lft forever
16: dummy0: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
    link/ether fe:e1:d0:a1:42:89 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::fce1:d0ff:fea1:4289/64 scope link
       valid_lft forever preferred_lft forever
 
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