Hello I recently noticed a weird problem I was experiencing in my xen setup. I''m actually not sure if the problem was with Xen, or with linux bridging, but I want to let everyone here know, in case others have the same problem. My dom0 is running Xen3.0.1 on Ubuntu 5.10, with two physical nics. One nic, eth0 is for management, ssh access to dom0, nfs traffic, etc. The other nic, eth1, is for all domU traffic. It is in promisc. mode, passing all traffic to the bridge, xenbr0. The problem I was experiencing was that some domUs would not be able to get through to the outside. I ran tcpdump on eth1, xenbr0, and vif1.1 (or whatever the appropriate vif was for the domain in question). The packets would appear on vif1.1, but not xenbr0 or eth1. However, some domUs would work fine, and their packets would show up on all three appropriate places. I traced the problem to the MAC addresses. I need to specify mac addresses for overall management on the greater network, but it doesn''t matter (to me or the network admin) what they are, as long as they are unique on the network. It turns out that addresses starting with 11:13 - 11:17 don''t work. (There are probably other ranges that don''t work, but that is all I tested.) According to http://standards.ieee.org/regauth/oui/oui.txt those addresses are not assigned (though they are also not reserved for private use, or for Xen), and I know that they are not in use on my network. I changed the MAC addresses for the hosts that didn''t work to a range that I know works, and everything is fine. Does anyone know why this happened? In any case, I hope this info can save some other people a few headaches. -Patrick _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Patrick Kaeding schrieb:> Hello > > I recently noticed a weird problem I was experiencing in my xen setup. > I''m actually not sure if the problem was with Xen, or with linux > bridging, but I want to let everyone here know, in case others have > the same problem. > > My dom0 is running Xen3.0.1 on Ubuntu 5.10, with two physical nics. > One nic, eth0 is for management, ssh access to dom0, nfs traffic, etc. > The other nic, eth1, is for all domU traffic. It is in promisc. > mode, passing all traffic to the bridge, xenbr0. > > The problem I was experiencing was that some domUs would not be able > to get through to the outside. I ran tcpdump on eth1, xenbr0, and > vif1.1 (or whatever the appropriate vif was for the domain in > question). The packets would appear on vif1.1, but not xenbr0 or > eth1. However, some domUs would work fine, and their packets would > show up on all three appropriate places. > > I traced the problem to the MAC addresses. I need to specify mac > addresses for overall management on the greater network, but it > doesn''t matter (to me or the network admin) what they are, as long as > they are unique on the network. It turns out that addresses starting > with 11:13 - 11:17 don''t work. (There are probably other ranges that > don''t work, but that is all I tested.) According to > http://standards.ieee.org/regauth/oui/oui.txt those addresses are not > assigned (though they are also not reserved for private use, or for > Xen), and I know that they are not in use on my network. I changed > the MAC addresses for the hosts that didn''t work to a range that I > know works, and everything is fine. > > Does anyone know why this happened? > > In any case, I hope this info can save some other people a few headaches. > > -Patrick > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users > >Did you try tcpdump -vv ?? You will see a lot of checksum errors. I had other very very weird problems with XEN networking in 3.0.1 and 3.0.2 (also with Ubuntu 5.10) It is a bug in xen. The current workarround is entering ethtool -K eth<0-n> tx off in each domU for each available interface. I did it automatically by writing post-up ethtool -K eth0 tx off into /etc/network/interfaces of each domU. Maybe this will work for you too. Regards Flori _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users