On Fri, 2006-07-21 at 16:40 -0600, Michael L Torrie wrote: > I hope someone out there has a bit of xen experience and can enlighten > me on a networking issue. > > I installed Fedora Core 5 and proceeded to install the xen kernels and > toolkits. After rebooting into the Xen dom0 kernel, I find that the > machine can no longer communicate over the network. After doing some > sniffing and digging I found that the reason for this is that packets > are going out of the ethernet interface with a source address of > FF:FF:FF:FF:FF:FF, which is the default mac address assigned to the xen- > specific peth0 interface. I have another xen host (FC4) that apparently > had done the same thing, so now that there were two machines on the > network with the same mac address (FF:FF:FF:FF:FF:FF), packets no longer > travel correctly. From what I've read, this mac address needn't be > changed because it's an internal mac address and that address should > never make it out on the wire (the real interface's mac address would be > used for dom0). This is very confusing and the docs on xen networking > are not very good.
That is correct. The only addresses you should see on the wire are those of the physical hardware in Dom0 (Xen doesn't mess with them) and the virtual ethXs in each of your DomUs. All of the other stuff is for internal use only (DomX to DomX and loopback). I just took a look at one of the Xen installs that I have running and verified this to be true (well, at least in my case :)). I don't know what's happening, but it seems like something must have been mixed up in the install. > Is this normal for the dom0 packets to go out with the FF:FF:FF:FF:FF:FF > address? I can't think it is, as that is supposed to be an ethernet > broadcast address. I haven't altered any configs at all yet. This is > an out-of-the-box FC5 install. Any advice is appreciated. What tool(s) were you using to view the traffic? I just sshed from my Dom0 and DomU into a non-Xen box to establish a connection and then checked the arp tables on the non-Xen box. I guess that wouldn't detect the presence of FF:FF:FF:FF:FF:FF on the wire, but is does show that a working setup uses the hardware address you would expect. It can get confusing figuring out what is going where on the actual Xen box when you are dealing with this: [EMAIL PROTECTED]:~# ifconfig | grep HWaddr eth0 Link encap:Ethernet HWaddr 00:06:5B:0F:0E:42 peth0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF vif0.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF vif24.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF vif33.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF vif36.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF vif44.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF vif44.1 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF vif44.2 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF xenbr0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF Anyway, good luck and let us know what you learn. Gabe /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
