Thanks, Sasikanth, for your response. Yes, I didn't realize that we need a MAC address for STP. Not 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 Szcześniak <irek.szczesniak@xxxxxxxxx > <mailto:irek.szczesniak@xxxxxxxxx>> > > Hi, > > I have a few questions on the Linux bridge, and I would appreciate it > if someone could answer them. > > 1. Why does a bridge have a MAC address? A bridge doesn't need a MAC > address. I understand that a Linux box might offer more than a regular > switch, and for that you need a MAC address. But the services should > > Yes, Linux bridge needs mac address. Because linux works based on > the 802.1D bridge > which has MAC relay entity, Spanning tree protocol entity. The > bridge required mac-address to communicate > with other bridges. For example to form a loop-free network > spanning-tree protocol in the bridges will communicate with > the bridges using BPDU, the bpdus carry the bridge address to > identify from which bridge we have received the BPDU. > If your bridge just acts as forwarding agent, then mac address is > not requried. > > be provided by a new tap interface added to the bridge. I believe that > the bridge should not even be shown by ifconfig. > > > I am not familiar with tap interface, So ignoring it. > I agree with you that bridge should not be shown in ifconfig. > Bridge must come up when anyone of the bridge ports are up. > But in current implementation we have to issue ifconfig <bridge> > up to make the bridge up. As far as i see it is not required. > Hope someone can give more clarification and its purpose > > > 2. Why does a bridge take the lowest MAC address of the interfaces > connected to it? > > > From 802.1D > > 7.12.5 Unique identification of a bridge > A unique 48-bit Universally Administered MAC Address, termed the > Bridge Address, shall be assigned to > each Bridge. The Bridge Address may be the individual MAC > Address of a Bridge Port, in which case, use > of the address of the lowest numbered Bridge Port (Port 1) is > recommended. > > > 3. When I send broadcast frames to a bridge interface (etherwake -b -i > br0 00:00:00:00:00:00), the frames are received by the interfaces of > the bridge. But when I send the frames to one of the interfaces, they > are not broadcasted to other interfaces. I though that the bridge > interface (br0) behaves the same as an interface added to the bridge, > but I was mistaken. What are the differences? > > no idea > > > Thanks, > Irek > > -- > Ireneusz (Irek) Szczesniak > http://www.irkos.org > _______________________________________________ > Bridge mailing list > Bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx > <mailto:Bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx> > 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
