[SOLVED] NAT MASQUERADING Not Working! Please Help!

freddyfunkalicious

New Member
Jan 9, 2025
4
0
1
So I am about ready to give up on PROXMOX...
I've spent more than 10 hours trying to get internet connectivity to my NAT'd Guest VMs, I've read literally every post on the internet, ive rebooted the server a dozen times and shutdown the guests many dozens... I've even sat through multiple OS reinstallations, all to no avail. I have four guest VMs: Ubuntu 24, Kali, Win 10 and WinServer 2019, each configured with static IPs on the 10.10.10.0/24 subnet. All the firewalls have been turned off (that I can find) and the guests can all ping each other and the PROXMOX host. However, none of the guests have internet access.

PROXMOX interfaces:

auto lo
iface lo inet loopback

auto eno1
iface eno1 inet manual
iface eno2 inet manual
iface eno3 inet manual
iface eno4 inet manual

auto vmbr0
iface vmbr0 inet static
address 192.168.88.123/24
gateway 192.168.0.1
bridge-ports eno1
bridge-stp off
bridge-fd 0

auto vmbr1
iface vmbr1 inet static
address 10.10.10.1/24
bridge-ports none
bridge-stp off
bridge-fd 0

post-up echo 1 > /proc/sys/net/ipv4/ip_forward
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
post-up iptables -t raw -I PREROUTING -i fwbr+ -j CT --zone 1
post-down iptables -t raw -D PREROUTING -i fwbr+ -j CT --zone 1
source /etc/network/interfaces.d/*

Ubuntu Guest Netplan:

network:
version: 2
ethernets:
ens18:
dhcp4: no
dhcp6: no
addresses: [10.10.10.25/24]
routes:
- to: default
via: 10.10.10.1
nameservers:
addresses: [8.8.8.8,8.8.4.4]

Ubuntu IP ROUTE:
default via 10.10.10.1 dev ens18 proto static metric 20100
10.10.10.0/24 dev ens18 proto kernel scope link src 10.10.10.25 metric 100
 
I think my issue may be an upstream issue. The server itself is not getting internet access, however if I put a VM on VMBR0 it DOES get internet access.
 
All right! Fixed...
The main problem was that i had the wrong gateway specified in my proxmox interfaces. I was specifying my external router (192.168.0.1), not my internal router (192.168.88.1).

auto vmbr0
iface vmbr0 inet static
address 192.168.88.123/24
gateway 192.168.88.1
bridge-ports eno1
bridge-stp off
bridge-fd 0
 
The weird thing is that all the VMs I assigned to vmbr0 worked fine, but the host itself and the vms I assigned to vmbr1 did NOT work...
 

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