I have here an experimental Windows7 system which interconnects two ethernet segments with network bridging.

It works like charm, but... it substitutes the MAC addresses of the forwarded packets with its own. This is not a bridge function, looks much more like an arp proxying router.

More exactly:

segment1 <--> Win7 <--> segment2

If I send a packet from segment1 to segment2, it is perfectly forwarded, but the receiver on segment2 sees the MAC address of the Win7, and not the MAC of the original sender!

Why is it? Is there any workaround? Maybe an alternative software?

  • Are both segments wired Ethernet? This behavior would be pretty much required if bridging Wi-Fi without WDS. – user1686 Jun 8 '16 at 4:49
  • No, what you say is NOT a switch, but a proxy arp. It is not "required behavior", it is not a switch. Wds hasn't anything to do with that, it is not about wireless headers, it is about that mac addresses are overwritten by the miniport "switch". Btw, bridging two ethernet segments does the same behavior. – peterh - Reinstate Monica Jun 8 '16 at 5:03
  • Well, if it were Wi-Fi, then the bridge would have to overwrite MAC addresses because that is in fact required by the wireless headers. (Well, unless you're an AP.). If it's Ethernet-only, then no, that's not required. – user1686 Jun 8 '16 at 5:04
  • @grawity Well, here is a simple description, what is a bridge: en.m.wikipedia.org/wiki/File:Network_Bridging.png . And: 1) a similar configuration works perfectly with Linux 2) bridging 2 ethernet segments with the windows miniport bridge behaves the same. MAC overwrite isn't needed in any cases, where did you get this? – peterh - Reinstate Monica Jun 8 '16 at 5:14
  • @grawity And finally: a "bridge" which overwrites MAC is not a bridge. It is a router. – peterh - Reinstate Monica Jun 8 '16 at 5:23

If segment2 is Wi-Fi, packets from clients in segment1 with their original MAC addresses will be dropped by the wireless AP in segment2 since these MAC addresses have no Wi-Fi association with the AP. Substitution of the MAC addresses at Win7 is one practical solution, no matter if you still want to call it bridging.

  • 2
    Not I call it bridging, the microsoft calls it bridging. What it is not. It is not a "practical solution", it is some different thing what it is called. – peterh - Reinstate Monica Jan 15 '19 at 13:23

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