Is there a way to set up Linux as an Ethernet repeater?

garage_greg

Is there a way to configure two Ethernet interfaces in a Linux box to work as an Ethernet repeater ? I.e. what goes in one interface would immediately go out from the other. I know there is bridging, but I would like an even more direct forwarding of all traffic , including the reserved MAC addresses starting from 01:80:C2:00:00:00 . And it would be nice if Wireshark could capture all that data.

Originally asked by Kalle Pokki on Stack Exchange (superuser) (CC BY-SA 4.0).

uphilltech

Great question — answering as the UphillTech team:

Linux can be configured to allow forwarding some of those addresses, but not all of them. In particular, you can't enable forwarding of 00 / 01 / 02 (STP and LACP frames). The rest (things like LLDP) can be enabled through /sys/class/net/br0/bridge/group_fwd_mask , e.g. setting it to 248 to enable transparent forwarding for everything except the three aforementioned groups. For full forwarding, you might need to make something in userspace instead – i.e. instead of a bridge, run a process to manually copy frames between two separate interfaces: socat interface:eth0 interface:eth1 Alternatively, find an Ethernet switch that supports "L2 protocol tunneling" (at least that's what TP-Link calls...

Full answer by grawity: https://superuser.stackexchange.com/a/1771490 (CC BY-SA 4.0).

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