It is normal for switch vendors to assign mac addresses to a bridge - only cheap consumer bridges don't have them, normally this is assigned by a stanza during config. I think many of these problems come from the fact that bridge devices in linux are really more like a SAP construct. It would be more useful IMHO to introduce a new class of "bridge" device which acted like a SAP (service access port) Consider: Customer A - CVLAN 100 Customer B - CVLAN 200 Service A - SVLAN 1000 Service B - SVLAN 2000 Incoming interface received QinQ (stacked) 1000:[100-200] as both subscribers are on service 1000. To get both of these customers to be in the same segment you first need to create a bridge, create a vlan 1000, then each CVLAN per customer off this new interface, and finally add it to the bridge. Tunable like per bridge member interface broadcast enable/disable etc would be nice as well. A SAP construct would allow alot more flexibility and I think clear up some of the uses that bridge devices are currently used for. 2011/4/26 Ireneusz SzczeÅniak <irek.szczesniak@xxxxxxxxx>: > Thanks, Sasikanth, for your response. ÂYes, I didn't realize that we > need a MAC address for STP. ÂNot only we need a MAC for a bridge, but > there can be MAC addresses for ports too, and why I just don't know. > I need to do some reading on STP, because I know very little about it. > > On 25.04.2011 13:02, Sasikanth V wrote: >> 2011/4/25 Ireneusz SzczeÅniak <irek.szczesniak@xxxxxxxxx >> <mailto:irek.szczesniak@xxxxxxxxx>> >> >> Â Â Hi, >> >> Â Â I have a few questions on the Linux bridge, and I would appreciate it >> Â Â if someone could answer them. >> >> Â Â 1. Why does a bridge have a MAC address? ÂA bridge doesn't need a MAC >> Â Â address. I understand that a Linux box might offer more than a regular >> Â Â switch, and for that you need a MAC address. But the services should >> >> Â Â ÂYes, Linux bridge needs mac address. Because linux works based on >> the 802.1D bridge >> Â Â Âwhich has MAC relay entity, ÂSpanning tree protocol entity. The >> bridge required mac-address to communicate >> Â Â Âwith other bridges. For example to form a loop-free network >> spanning-tree protocol in the bridges will communicate with >> Â Â Âthe bridges using BPDU, the bpdus carry the bridge address to >> identify from which bridge we have received the BPDU. >> Â Â ÂIf your bridge just acts as forwarding Âagent, then mac address is >> not requried. >> >> Â Â be provided by a new tap interface added to the bridge. I believe that >> Â Â the bridge should not even be shown by ifconfig. >> >> >> Â Â ÂI am not familiar with tap interface, So ignoring it. >> Â Â ÂI agree with you that bridge should not be shown in ifconfig. >> Bridge must come up Âwhen anyone of the bridge ports are up. >> Â Â ÂBut in current implementation we have to issue ifconfig <bridge> >> up Âto make the bridge up. As far as i see it is not required. >> Â Â ÂHope someone can give more clarification and its purpose >> >> >> Â Â 2. Why does a bridge take the lowest MAC address of the interfaces >> Â Â connected to it? >> >> >> Â Â Â Â From 802.1D >> >> Â Â Â Â 7.12.5 Unique identification of a bridge >> Â Â Â Â A unique 48-bit Universally Administered MAC Address, termed the >> Bridge Address, shall be assigned to >> Â Â Â Â each Bridge. The Bridge Address may be the individual MAC >> Address of a Bridge Port, in which case, use >> Â Â Â Â of the address of the lowest numbered Bridge Port (Port 1) is >> recommended. >> >> >> Â Â 3. When I send broadcast frames to a bridge interface (etherwake -b -i >> Â Â br0 00:00:00:00:00:00), the frames are received by the interfaces of >> Â Â the bridge. ÂBut when I send the frames to one of the interfaces, they >> Â Â are not broadcasted to other interfaces. ÂI though that the bridge >> Â Â interface (br0) behaves the same as an interface added to the bridge, >> Â Â but I was mistaken. ÂWhat are the differences? >> >> Â Â Âno idea >> >> >> Â Â Thanks, >> Â Â Irek >> >> Â Â -- >> Â Â Ireneusz (Irek) Szczesniak >> Â Â http://www.irkos.org >> Â Â _______________________________________________ >> Â Â Bridge mailing list >> Â Â Bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx >> Â Â <mailto:Bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx> >> Â Â https://lists.linux-foundation.org/mailman/listinfo/bridge >> > > > -- > Ireneusz (Irek) Szczesniak > http://www.irkos.org > _______________________________________________ > Bridge mailing list > Bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx > https://lists.linux-foundation.org/mailman/listinfo/bridge > _______________________________________________ Bridge mailing list Bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/bridge
