On Sat, 16 Dec 2017 16:19:03 +0200 Adrian P <adrian27oradea@xxxxxxxxx> wrote: > Investigating this further, I have noticed that the mac address of the > eth0 interface from the cirros VM instance does not appear in the > bridge forwarding table, and this explains why everything starts > working only when I set ageing time to 0, because in that case all > packets are flooded on all ports and the bridge behaves like a hub. > > So now the question is: why the bridge does not learn the mac address > of the eth0 interface from the cirros VM instance? I am able to see > the arp request (ARP, Request who-has 10.20.21.1 tell 10.20.21.233) > going out from the cirros VM instance on tap interface, so the bridge > should learn the mac address and add it to the forwarding table. > > The reply back to the arp request (Reply 10.20.21.1 is-at > 00:17:08:c4:52:80) does not reach the cirros VM instance anymore, and > now I know why: there is no mac address in the forwarding table, so > the bridge does not know on which port to send the arp reply back. > > This happens with tap interfaces only. I can see many mac addresses > associated with "physical" interface ens160 (that is interface number > 1) in the forwarding table, but in case of the tap interfaces, there > are only two entries, and both entries shows the mac address of the > tap interfaces only: VMWare does ARP spoofing maybe it consumes the ARP
