Andreas Bach Aaen (AH/TED)
2005-Sep-08 11:03 UTC
[Xen-users] Switches and a moving MAC address
Hi, I have a succesfull XEN 2.06 installation with a DomU running with it''s rootfs over NFS. I can migrate this GuestOS between hosts on the same switches network. I connect to my GuestOS over tcp (ssh). The transfer of the GuestOS takes about 4 seconds, and with the live option it should be for a very short period where the GuestOS actually is stopped. After the transfer it takes 20-30 seconds before the GuestOS becomes responsive again. Which kind of timeout it this? When you move an IP address to another MAC address you typically send out an unsolicited ARP to update the arp caches on the other hosts on the network to ensure correct routing at once. Are there any similar thing I could do to make sure that the switch will broadcast the next packet for the MAC address that suddenly has moved to another port? Regards, -- Andreas Bach Aaen System Developer, M. Sc. Ericsson Danmark A/S tel: +45 89 38 51 00 Skanderborgvej 232 fax: +45 89 38 51 01 8260 Viby J Denmark andreas.bach.aaen@ericsson.com _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
If I understand the way the XEN migration works, though, the MAC address of the guest O/S moves with the guest O/S to the new host machine (assuming, of course, that you''re using virtual interfaces with Linux bridging). Otherwise I don''t think that the live migration would work very well, as routers, switches, and even the PC''s that are connecting to the guest O/S would have to learn a new MAC address. This would cause a loss of network connectivity longer than the fractions of a second that you lose when you migrate. If you''re using PCI devices in guest O/S, then you have an entirely different problem and you probably want to set your own MAC address on those devices so that it can migrate with the guest O/S. (Some of the actual experts on this list might want to chime in with their two bits - I''m fairly new to XEN, so I''m just going off what I understand from documentation, other thread, etc. Anyone else care to provide input?) Nick Couchman Systems Integrator SEAKR Engineering, Inc. 6221 South Racine Circle Centennial, CO 80111 Main: (303) 790-8499 Fax: (303) 790-8720 Web: http://www.seakr.com>>> "Andreas Bach Aaen (AH/TED)" <andreas.bach.aaen@ericsson.com> 2005/09/08 05:03:27 >>>Hi, I have a succesfull XEN 2.06 installation with a DomU running with it''s rootfs over NFS. I can migrate this GuestOS between hosts on the same switches network. I connect to my GuestOS over tcp (ssh). The transfer of the GuestOS takes about 4 seconds, and with the live option it should be for a very short period where the GuestOS actually is stopped. After the transfer it takes 20-30 seconds before the GuestOS becomes responsive again. Which kind of timeout it this? When you move an IP address to another MAC address you typically send out an unsolicited ARP to update the arp caches on the other hosts on the network to ensure correct routing at once. Are there any similar thing I could do to make sure that the switch will broadcast the next packet for the MAC address that suddenly has moved to another port? Regards, -- Andreas Bach Aaen System Developer, M. Sc. Ericsson Danmark A/S tel: +45 89 38 51 00 Skanderborgvej 232 fax: +45 89 38 51 01 8260 Viby J Denmark andreas.bach.aaen@ericsson.com _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Andreas Bach Aaen (AH/TED) schrieb:>Hi, > >I have a succesfull XEN 2.06 installation with a DomU running with it''s rootfs >over NFS. I can migrate this GuestOS between hosts on the same switches >network. I connect to my GuestOS over tcp (ssh). >The transfer of the GuestOS takes about 4 seconds, and with the live option it >should be for a very short period where the GuestOS actually is stopped. >After the transfer it takes 20-30 seconds before the GuestOS becomes >responsive again. Which kind of timeout it this? > >When you move an IP address to another MAC address you typically send out an >unsolicited ARP to update the arp caches on the other hosts on the network to >ensure correct routing at once. >Are there any similar thing I could do to make sure that the switch will >broadcast the next packet for the MAC address that suddenly has moved to >another port? > >Do you migrate your domU together with a fixed MAC address or is it chosen by xend? Dirk _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Andreas Bach Aaen (AH/TED)
2005-Sep-09 06:52 UTC
Re: [Xen-users] Switches and a moving MAC address
On Fredag 09 september 2005 08:18, Dirk H. Schulz wrote:> Do you migrate your domU together with a fixed MAC address or is it > chosen by xend?Yes I do move my DomU with a fixed MAC address. I want to make the package dropping period in the switch between the two physical hosts as small as possible. Hence I would like to flush the forwarding cache in the switch for this particular MAC address. If the DomU sens a package emidiately after its transfered then the switch will be updated and packages send to it wont be send to its old location. As you don''t want to disturb the DomU for the transfer then the package could be send from dom0 with the domU MAC address as source. Regards, -- Andreas Bach Aaen System Developer, M. Sc. Ericsson Danmark A/S tel: +45 89 38 51 00 Skanderborgvej 232 fax: +45 89 38 51 01 8260 Viby J Denmark andreas.bach.aaen@ericsson.com _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> > Do you migrate your domU together with a fixed MAC address or is it > > chosen by xend? > > Yes I do move my DomU with a fixed MAC address. > I want to make the package dropping period in the switch > between the two physical hosts as small as possible. > Hence I would like to flush the forwarding cache in the > switch for this particular MAC address. > If the DomU sens a package emidiately after its transfered > then the switch will be updated and packages send to it wont > be send to its old location. > As you don''t want to disturb the DomU for the transfer then > the package could be send from dom0 with the domU MAC address > as source.This should already happen, at least it used to on 2.0. Might be worth veryifying the code hasn''t rotted. We send an unsolicited arp reply, which works in both the case of moving the MAC and of moving just the IP. (The source mac address of the packet should cause the switch to reconfigure.) Ian _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Andreas Bach Aaen (AH/TED)
2005-Sep-09 09:59 UTC
Re: [Xen-users] Switches and a moving MAC address
On Fredag 09 september 2005 11:11, Ian Pratt wrote:> > Hence I would like to flush the forwarding cache in the > > switch for this particular MAC address. > This should already happen, at least it used to on 2.0. Might be worth > veryifying the code hasn''t rotted. > > We send an unsolicited arp reply, which works in both the case of moving > the MAC and of moving just the IP. (The source mac address of the packet > should cause the switch to reconfigure.)Right. Maybe the code in: /usr/lib/python2.3/site-packages/xen/xend/XendDomainInfo.py where the comment says: """send an unsolicited ARP reply for all non link-local IP addresses. Regards, -- Andreas Bach Aaen System Developer, M. Sc. Ericsson Danmark A/S tel: +45 89 38 51 00 Skanderborgvej 232 fax: +45 89 38 51 01 8260 Viby J Denmark andreas.bach.aaen@ericsson.com _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users