TAP bridge and ports

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thisisliam
OpenVpn Newbie
Posts: 9
Joined: Wed Aug 02, 2023 1:41 am

TAP bridge and ports

Post by thisisliam » Thu Jan 11, 2024 4:23 am

Hi all. I seem to have [finally] successfully created a TAP bridge through two remote routers running OpenWRT. I can plug into the eth0 port on my client router, receive an IP address from the server, see network devices on the server side and access the internet through the tunnel. Both ends are on gigabit fiber. No issues at all so far.

This setup is dedicated purely for two multimedia devices to communicate over the internet that require broadcast and multicast traffic, therefore TAP is required. I'm not concerned about bandwidth being hogged or system resources on the router - with the current bridge I'm not having any problems when it comes to resources. As I said, the internet connection and routers have been installed purely for this setup.

When I connect the multimedia device on the client side, it receives an IP as expected and can "see" the internet but it's not "connecting" to the device on the server router. I have run ARP commands and can see there is chatter there between the two devices but alas the "appropriate" connection isn't being made - this makes me suspect perhaps an issue with the broadcast and multicast traffic.

A user on another board told me I need to set further firewall rules to allow both broadcast and multicast traffic to pass through on the server side. In my preparation for this project I was under the impression that TAP mode allowed this without further separate router configuration outside of creating firewall rules for OpenVPN itself. I was given this as an example for the firewall:

Code: Select all

config rule
    option name 'Allow OpenVPN Broadcast/Multicast'
    option src 'lan'   #Replace with your OpenVPN zone
    option dest_port '67 68'   #Replace with the appropriate port numbers for DHCP
    option proto 'udp'
    option target 'ACCEPT'
I'm wondering if anyone might be able to shed light on how multicast/broadcast traffic traverses a TAP bridge/tunnel so I can figure out the final steps to making this work. If necessary I can provide server/client config files.

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