# How does it work - ethernet - vlan - bridge - tap flow



## slowmok (Apr 22, 2019)

Hello! I need some help with understanding some base things.
I have FreeBSD virtual machine on Windows host with VirtualBox. At FreeBSD machine running OpenVPN client with Tap confuguratin (cant use Tun for some reasons).
interfaces: em0 - external connection and local network with host PC 192.168.0.0/24
tap0 - OpenVPN 10.8.0.0/24
bridge0 - tap/vlan inteface
Vlan1  - network for OpenVPN machines 10.0.212.0/24

OpenVPN work perfectly from FreeBSD machine

I want use FreeBSD as gateway for PC Windows 7 host machine.
1. Add route at Windows Host to FreeBSD em0 IF
2. Turnd on forwarding on FreeBSD/enabled gateway

Help me please understand packet flow from windows host through em0 - tap0 interfaces. How does it work?

netstat:
default            192.168.0.1        UGS         em0
10.0.212.0/24      link#4             U         vlan1
10.0.212.226       link#4             UHS         lo0
10.8.0.0/24        link#3             U          tap0

If i ping 10.0.212.1 from win host, i can cee incoming traffic in Tcpdump -i em0, also in Tcpdump -i tap0, but nothing at Tcpdump -i Vlan1. Why? How does it work? i didnt see route 10.0.212.0/24 via tap0. I thought it should be "em0 - vlan1 - bridge0 - tap0" but it work like "em0 - tap0" without "- valn- bridge -"

Seems i didnt understand some basics with bridging but cant find answers.

I am newbie at FreeBSD. Manuals didnt get answer to me (may be i cant find answer because of my bad english). SO i will be 
appreciate for any help.


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## SirDice (Apr 25, 2019)

slowmok said:


> If i ping 10.0.212.1 from win host, i can cee incoming traffic in Tcpdump -i em0, also in Tcpdump -i tap0, but nothing at Tcpdump -i Vlan1. Why?


Your traffic is _untagged_.






						IEEE 802.1Q - Wikipedia
					






					en.wikipedia.org


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## slowmok (Mar 3, 2020)

Thx for answer!


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