OpenVPN bridge mode with only public interface

This forum is for admins who are looking to build or expand their OpenVPN setup.
Forum rules
Please use the [oconf] BB tag for openvpn Configurations. See viewtopic.php?f=30&t=21589 for an example.
Post Reply
LgWagon
OpenVpn Newbie
Posts: 1
Joined: Sat Dec 03, 2022 11:48 am

OpenVPN bridge mode with only public interface

Post by LgWagon » Sat Dec 03, 2022 12:26 pm

Dear all,
I am in torouble setting OpenVPN bridge mode for testing on my linux VPS. The machine has only an eth0 interface with a public IP (i.e: 103.248.76.252, with gateway 103.248.76.1). Obviously, when I create the bridge between the TAP NIC and eth0 I loose connectivity, and I have no more access via SSH to the server. Beside this, I don't like the idea to create a bridge with a public interface. I've tried to create a virtual NIC, named eth1, bridging the TAP NIC to eth1, and forwarding all the traffic from eth0 to eth1, inside the bridge. However, also in this case it doesn't work.
Here are results of ifconfig:

br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.1.100 netmask 255.255.255.0 broadcast 192.168.1.255
inet6 prefixlen 64 scopeid 0x20<link>
ether **:**:**:**:**:** txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 10 bytes 924 (924.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 103.248.76.252 netmask 255.255.255.0 broadcast 103.248.76.255
inet6 prefixlen 64 scopeid 0x20<link>
ether **:**:**:**:**:** txqueuelen 1000 (Ethernet)
RX packets 35512 bytes 7531978 (7.5 MB)
RX errors 0 dropped 5269 overruns 0 frame 0
TX packets 10852 bytes 1522647 (1.5 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

eth1: flags=451<UP,BROADCAST,RUNNING,NOARP,PROMISC> mtu 1500
inet6 prefixlen 64 scopeid 0x20<link>
ether **:**:**:**:**:** txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 34 bytes 2828 (2.8 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 404 bytes 29088 (29.0 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 404 bytes 29088 (29.0 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

tap0: flags=4355<UP,BROADCAST,PROMISC,MULTICAST> mtu 1500
ether **:**:**:**:**:** txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

Here are my routes:
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 103.248.76.1 0.0.0.0 UG 100 0 0 eth0
103.248.76.0 0.0.0.0 255.255.255.0 U 100 0 0 eth0
103.248.76.1 0.0.0.0 255.255.255.255 UH 100 0 0 eth0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 br0

What am I missing? Thanks in advance..
Lg

User avatar
ordex
OpenVPN Inc.
Posts: 437
Joined: Wed Dec 28, 2016 2:32 am
Location: IRC #openvpn-devel @ libera.chat

Re: OpenVPN bridge mode with only public interface

Post by ordex » Tue Dec 06, 2022 10:51 am

Hi there! How about explaining what you are trying to achieve?
It is not clear what you want to do and why you need a bridge.

Post Reply