Virtualization and Network Configuration in PVE

[laniatus]

Dear Proxmox Community,

We are a cloud game technology company. We previously had servers in Cogent and due to administrative problems, we made another decision and moved to Hetzner.
But we couldn't get a response from Hetzner's support system, so we ended up here. We are having a problem on our Proxmox server, this problem we are experiencing is briefly network assignment to VMs. First of all, I will briefly explain the problem we are experiencing.

In our node, VM number 108 has Windows installed. The network configuration of the VM is as follows.

In this server, the network assignment is done and the server is going online. The VM configuration of the server is as follows;

The network configuration on the node side is also like this. (Linux Bridge)

Now that we have come this far, this is our IPs configuration in Robot.

Now my question is generally as follows; According to the network configuration on the Windows server, we assign an IP in our subnets to Centos 5.8, but the VM does not ping. The same configuration is provided as below.

Details about the VM that did not go online are below.

RESULT

Since we really cannot solve the problem, we have to ask for your valuable opinions. If you can help, we would really appreciate it. Unfortunately, even though our configurations are correct, we cannot out on to the internet. By the way, our server in Robot is a direct migrated backup from Cogent. So the servers running there, as you can see, we can't access the internet in Hetzner at the moment.

 

[gurubert]

Is the subnet 178… routed to your 94… IP?
Or is it available on the Ethernet LAN and Hetzner does the routing?

Have you enabled IP forwarding in the Proxmox kernel? Have a look at /etc/sysctl.conf

 

[laniatus]

Is the subnet 178… routed to your 94… IP?
Or is it available on the Ethernet LAN and Hetzner does the routing?

Have you enabled IP forwarding in the Proxmox kernel? Have a look at /etc/sysctl.conf

Hello, thank you for your precious time. Yes, Hetzner routes the subnet in the robot, otherwise the Ethernet would not come to the Windows server. This problem only applies to Linux. Here below is the configuration of our sysctl.conf file.

Subnet conf

94.xxxxx.84 is proxmox's ip, so yeah, I think so.

Spoiler: PVE server sysctl.conf

#
# /etc/sysctl.conf - Configuration file for setting system variables
# See /etc/sysctl.d/ for additional system variables.
# See sysctl.conf (5) for information.
#

#kernel.domainname = example.com

# Uncomment the following to stop low-level messages on console
#kernel.printk = 3 4 1 3

###################################################################
# Functions previously found in netbase
#

# Uncomment the next two lines to enable Spoof protection (reverse-path filter)
# Turn on Source Address Verification in all interfaces to
# prevent some spoofing attacks
#net.ipv4.conf.default.rp_filter=1
#net.ipv4.conf.all.rp_filter=1

# Uncomment the next line to enable TCP/IP SYN cookies
# See http://lwn.net/Articles/277146/
# Note: This may impact IPv6 TCP sessions too
#net.ipv4.tcp_syncookies=1

# Uncomment the next line to enable packet forwarding for IPv4
#net.ipv4.ip_forward=1

# Uncomment the next line to enable packet forwarding for IPv6
# Enabling this option disables Stateless Address Autoconfiguration
# based on Router Advertisements for this host
#net.ipv6.conf.all.forwarding=1


###################################################################
# Additional settings - these settings can improve the network
# security of the host and prevent against some network attacks
# including spoofing attacks and man in the middle attacks through
# redirection. Some network environments, however, require that these
# settings are disabled so review and enable them as needed.
#
# Do not accept ICMP redirects (prevent MITM attacks)
#net.ipv4.conf.all.accept_redirects = 0
#net.ipv6.conf.all.accept_redirects = 0
# _or_
# Accept ICMP redirects only for gateways listed in our default
# gateway list (enabled by default)
# net.ipv4.conf.all.secure_redirects = 1
#
# Do not send ICMP redirects (we are not a router)
#net.ipv4.conf.all.send_redirects = 0
#
# Do not accept IP source route packets (we are not a router)
#net.ipv4.conf.all.accept_source_route = 0
#net.ipv6.conf.all.accept_source_route = 0
#
# Log Martian Packets
#net.ipv4.conf.all.log_martians = 1
#

###################################################################
# Magic system request Key
# 0=disable, 1=enable all, >1 bitmask of sysrq functions
# See https://www.kernel.org/doc/html/latest/admin-guide/sysrq.html
# for what other values do
#kernel.sysrq=438

 

[gurubert]

No I see a little glitch in your Linux VM's network configuration.
The GATEWAY setting cannot be the 94… IP address as the VM does not know how to reach it.
Instead configure the 178…41 IP address that resides on vmbr1 of the Proxmox host and enable IP forwarding.

I really do not know how Windows is able to use the 94… IP address as default gateway. Maybe it just sends an ARP request which is answered by the Proxmox host. I do not think that the Linux kernel will do something like this as it does not know where the 94… IP address should be.