I have a CentOS 5.2 Xen host, running several guest domains. Each guest domain has a single interface assigned to it. I am using both the network-bridge and vif-bridge scripts.

On my only windows guest, the tap interface connected to the bridge keeps getting disabled. If I check "brctl show" the tap0 interface is not present, and there will be several message log entries indicating that the interface tap0 is being disabled. This means that the guest becomes invisible. I can not open a VNC console or connect to it from the network. From the hosts log files, it appears that the OS keeps running, even though it it is unreachable. (this is a little hard to guage, because the times in the eventlog keep jumping around.) The only way I have been able to restore a connection is to destroy the domain and re-create it. I can not find much in the various Xen logs that identifies what triggers the tap interface to be disabled.

I have several questions.

Is there any way to manually rebuild the tap interface to get access to the host again (either through VNC or network)? Maybe through the virsh command or calling the vif-bridge or qemu-ifup command directly?

Is there another way that I could use to maintain a connection to the guest?

Does anyone have any idea what causes the tap interface to go down?

--qemu-dm log----------------------------------------------------

domid: 1 qemu: the number of cpus is 2 *** image /local/domain/0/backend/vbd/1/768 format raw driver 0x80e7940 *** image /local/domain/0/backend/vbd/1/5632 format raw driver 0x80e7940 *** image /local/domain/0/backend/vbd/1/832 format raw driver 0x80e7940 Watching /local/domain/1/logdirty/next-active xs_read(): vncpasswd get error. /vm/e2a537ca-5ef5-e87d-6505-855529af3ea4/vncpasswd. char device redirected to /dev/pts/1 qemu_map_cache_init nr_buckets = 4000 shared page at pfn 3ffff buffered io page at pfn 3fffd xs_read(/vm/e2a537ca-5ef5-e87d-6505-855529af3ea4/rtc/timeoffset): read error I/O request not ready: 0, ptr: 0, port: 0, data: 0, count: 0, size: 0 I/O request not ready: 0, ptr: 0, port: 0, data: 0, count: 0, size: 0 Triggered log-dirty buffer switch xs_write(/vm/e2a537ca-5ef5-e87d-6505-855529af3ea4/rtc/timeoffset, rtc/timeoffset): write error xs_write(/vm/e2a537ca-5ef5-e87d-6505-855529af3ea4/rtc/timeoffset, rtc/timeoffset): write error

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name = "vm-002_win" uuid = "e2a537ca5ef5e87d6505855529af3ea4" maxmem = 2048 memory = 1024 vcpus = 2 builder = "hvm" kernel = "/usr/lib/xen/boot/hvmloader" boot = "c" pae = 1 acpi = 1 apic = 1 on_poweroff = "destroy" on_reboot = "restart" on_crash = "restart" device_model = "/usr/lib/xen/bin/qemu-dm" sdl = 0 vnc = 1 vncunused = 1 keymap = "en-us" disk = [ "file:/var/lib/xen/images/vm-002_win.img,hda,w", "file:/data/os-install-media/Win2003plusSP1.iso,hdc:cdrom,r", "phy:/dev/VolGroup00/LVssavmWin001Data,hdb,w" ] vif = [ "ip=192.168.2.103,mac=00:16:3e:0d:7f:be,bridge=xenbr0,type=ioemu" ] serial = "pty"