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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?
peterh - Reinstate Monica
Posted 2016-06-08T03:17:42.173
Reputation: 2 043
Are both segments wired Ethernet? This behavior would be pretty much required if bridging Wi-Fi without WDS. – user1686 – 2016-06-08T04:49:20.763
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 – 2016-06-08T05:03:38.040
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 – 2016-06-08T05:04:46.290
@grawity Well, here is a simple description, what is a bridge: https://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 – 2016-06-08T05:14:31.630@grawity And finally: a "bridge" which overwrites MAC is not a bridge. It is a router. – peterh - Reinstate Monica – 2016-06-08T05:23:53.163
@grawity I suspect, poor microsoft couldn't implement a switch, because the team implementing this feature had to work with promisc mode interfaces. And so they emulated it with routing and with some arp trickery :-( – peterh - Reinstate Monica – 2016-06-08T05:27:15.413