[SOLVED] Linux Bridge on a public address

Jun 28, 2019
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For your information, here is my final configuration with an example of port forwarding to one of my VMs. I hope everything will be fine. Thank you again for your help

Code:
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet manual

# interface iface - public address interfae bridge
auto vmbr0
iface vmbr0 inet static
address 185.246.xx.xxx
netmask 255.255.255.0
gateway 185.246.xx.x
broadcast 185.246.xx.xxx
network 185.246.xx.x
bridge_ports eth0
bridge_stp off
bridge_fd 0

# internal iface - used to bridge VMs with invalid address with NAT
auto vmbr2
iface vmbr2 inet static
address 10.0.0.1
netmask 255.255.255.0
bridge_ports none
bridge_stp off
bridge_fd 0
post-up iptables -A POSTROUTING -t nat -s '10.0.0.0/24' -o vmbr0 -j MASQUERADE
post-up iptables -A POSTROUTING -t mangle -p udp --dport bootpc -j CHECKSUM --checksum-fill
post-up iptables -A FORWARD -s 10.0.0.0/24 -j ACCEPT
post-up iptables -t nat -A PREROUTING -p tcp --dport 23 -i vmbr0 -d 185.246.xx.xxx -j DNAT --to 10.0.0.11:22
post-up iptables -A FORWARD -p tcp --dport 23 -i vmbr0 -d 10.0.0.11 -j ACCEPT
post-down iptables -t filter -F
post-down iptables -t nat -F
post-down iptables -t mangle -F
Everything is fine*, my only advice is to not publish port 23 for outside, this port is frequently used for a lot kind of attacks, like DoS, portScan, etc... modify it for anything like 2222.

* Also, flushing the entire filter table of iptables on interface shutdown can lead to other side effects!! a lot of rules are created automatically by proxmox on filter table.
 

MarOwN

New Member
Nov 19, 2019
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Like this ?

Code:
post-up iptables -A POSTROUTING -t nat -s '10.0.0.0/24' -o vmbr0 -j MASQUERADE
post-up iptables -A POSTROUTING -t mangle -p udp --dport bootpc -j CHECKSUM --checksum-fill
post-down iptables -D POSTROUTING -t nat -s '10.0.0.0/24' -o vmbr0 -j MASQUERADE
post-down iptables -D POSTROUTING -t mangle -p udp --dport bootpc -j CHECKSUM --checksum-fill
post-up iptables -A FORWARD -s 10.0.0.0/24 -j ACCEPT
post-down iptables -D FORWARD -s 10.0.0.0/24 -j ACCEPT
post-up iptables -t nat -A PREROUTING -p tcp --dport 2xxx -i vmbr0 -d 185.246.87.214 -j DNAT --to 10.0.0.11:22
post-up iptables -A FORWARD -p tcp --dport 2xxx -i vmbr0 -d 10.0.0.11 -j ACCEPT
post-down iptables -D FORWARD -p tcp --dport 23 -i vmbr0 -d 10.0.0.11 -j ACCEPT
 

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