[SOLVED] Unable to access internet over Linux Bridge

[alexmak]

Hi,

We have started trying Proxmox recently (considering as an alternative to hyper-v), and are currently having some weird trouble to connect a VM and the internet.

We have two internet connections, the first one has a single public static ip and the second one has a block of public static ip.


The VM A can access the internet using connection from NIC1.
However, the same VM cannot access the internet using connection from NIC2.

I have tried the followings:
- Ping 1.1.1.1 from VM A NIC2 => Failed
- Ping Router B from VM A NIC2 => Successful
- Ping VM A NIC2 from another computer connected to Router B => Successful
- Ping 1.1.1.1 from another computer connected to Router B => Successful

It would be appreciated if anyone can share their insight about the issue.

Update:
Things get weirder as we tried installing a Windows Server VM. Under the same settings, the windows VM can actually access the internet.
The VM A mentioned is using Ubuntu 18.04 LTS.

 

[aaron]

Can you share the /etc/network/interfaces file of your Proxmox node and of the Ubuntu VM?

 

[alexmak]

Sure, here you are:

Proxmox node (/etc/network/interfaces)

# network interface settings; autogenerated
# Please do NOT modify this file directly, unless you know what
# you're doing.
#
# If you want to manage parts of the network configuration manually,
# please utilize the 'source' or 'source-directory' directives to do
# so.
# PVE will preserve these directives, but will NOT read its network
# configuration from sourced files, so do not attempt to move any of
# the PVE managed interfaces into external files!

auto lo
iface lo inet loopback

auto eno1
iface eno1 inet manual

auto eno2
iface eno2 inet manual

auto vmbr0
iface vmbr0 inet static
        address  172.16.0.100
        netmask  255.255.0.0
        gateway  172.16.0.1
        bridge-ports eno1
        bridge-stp off
        bridge-fd 0

auto vmbr1
iface vmbr1 inet manual
        bridge-ports eno2
        bridge-stp off
        bridge-fd 0

VM (/etc/netplan/50-cloud-init.yaml)

network:
    ethernets:
        ens18:
            addresses:
            - 172.16.0.110/16
            gateway4: 172.16.0.1
            nameservers:
                addresses:
                - 1.1.1.1
                - 1.0.0.1
        ens19:
            addresses:
            - 120.0.0.2/29
            gateway4: 120.0.0.1
            nameservers:
                addresses:
                - 1.1.1.1
                - 1.0.0.1
    version: 2

 

[spirit]

you have 2 default gateway in your vm, it's not possible. (only 1 will be used).

(or you need to play with multiple routing tables for each ip address)

 

[alexmak]

That solved the problem! Thank you

For people that may encounter this problem as well:
Just make sure that you have only one gateway defined, or configure static routing in netplan.

 

[aaron]

Great that we found the problem. Can you please mark the thread as solved? (Edit first posts title prefix)

 

[alexmak]

Done, thanks aaron and spirit.