I have a server running Centos 5.2 as a Xen host.  A problem that's 
shown up recently is that at boot, the dom0 interface eth0 doesn't come 
up properly, with the result that the host is only accessible via remote 
console.  If I execute 'service network restart', eth0 comes up 
normally, with an IP address and the correct routing.
Three guests have been created via virt-manager and I haven't changed 
any of the defaults, so I'm not sure what's causing this.
Here's ifconfig output after boot:
lo        Link encap:Local Loopback 
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:20 errors:0 dropped:0 overruns:0 frame:0
          TX packets:20 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:1308 (1.2 KiB)  TX bytes:1308 (1.2 KiB)
peth0     Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF 
          inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link
          UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
          RX packets:31844 errors:0 dropped:0 overruns:0 frame:0
          TX packets:15 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:4639017 (4.4 MiB)  TX bytes:4898 (4.7 KiB)
          Interrupt:16 Memory:da000000-da012100
vif0.0    Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF 
          inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link
          UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
          RX packets:24 errors:0 dropped:0 overruns:0 frame:0
          TX packets:31489 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:6891 (6.7 KiB)  TX bytes:4490222 (4.2 MiB)
virbr0    Link encap:Ethernet  HWaddr 00:00:00:00:00:00 
          inet addr:192.168.122.1  Bcast:192.168.122.255  Mask:255.255.255.0
          inet6 addr: fe80::200:ff:fe00:0/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:84 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 b)  TX bytes:16250 (15.8 KiB)
xenbr0    Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF 
          UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
          RX packets:31060 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:4035093 (3.8 MiB)  TX bytes:0 (0.0 b)
and again once I've restarted networking and have a guest running:
eth0      Link encap:Ethernet  HWaddr 00:1E:C9:CD:C7:0A 
          inet addr:10.99.91.151  Bcast:10.99.255.255  Mask:255.255.0.0
          inet6 addr: fe80::21e:c9ff:fecd:c70a/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:15836 errors:0 dropped:0 overruns:0 frame:0
          TX packets:10303 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:2136620 (2.0 MiB)  TX bytes:33113077 (31.5 MiB)
lo        Link encap:Local Loopback 
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:6676 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6676 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:33006844 (31.4 MiB)  TX bytes:33006844 (31.4 MiB)
peth0     Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF 
          inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link
          UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
          RX packets:63781 errors:0 dropped:0 overruns:0 frame:0
          TX packets:27001 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:9142626 (8.7 MiB)  TX bytes:34301305 (32.7 MiB)
          Interrupt:16 Memory:da000000-da012100
tap0      Link encap:Ethernet  HWaddr F2:C4:14:A0:43:50 
          inet6 addr: fe80::f0c4:14ff:fea0:4350/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:26853 errors:0 dropped:0 overruns:442 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:0 (0.0 b)  TX bytes:25995823 (24.7 MiB)
tap1      Link encap:Ethernet  HWaddr 96:9D:94:41:A1:C9 
          inet6 addr: fe80::949d:94ff:fe41:a1c9/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:26851 errors:0 dropped:0 overruns:443 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:0 (0.0 b)  TX bytes:25995669 (24.7 MiB)
vif0.0    Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF 
          inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link
          UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
          RX packets:10327 errors:0 dropped:0 overruns:0 frame:0
          TX packets:63318 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:33119968 (31.5 MiB)  TX bytes:8871385 (8.4 MiB)
vif1.0    Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF 
          UP BROADCAST NOARP  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:32
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
vif1.1    Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF 
          inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link
          UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
          RX packets:16 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8820 errors:0 dropped:1 overruns:0 carrier:0
          collisions:0 txqueuelen:32
          RX bytes:1584 (1.5 KiB)  TX bytes:24001390 (22.8 MiB)
virbr0    Link encap:Ethernet  HWaddr 00:00:00:00:00:00 
          inet addr:192.168.122.1  Bcast:192.168.122.255  Mask:255.255.255.0
          inet6 addr: fe80::200:ff:fe00:0/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:35 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 b)  TX bytes:10384 (10.1 KiB)
xenbr0    Link encap:Ethernet  HWaddr 96:9D:94:41:A1:C9 
          UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
          RX packets:53695 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:6909244 (6.5 MiB)  TX bytes:0 (0.0 b)
Adam Huffman wrote on Mon, 15 Dec 2008 14:21:36 +0000:> If I execute 'service network restart', eth0 comes up > normally, with an IP address and the correct routing.The network-scripts in the default CentOS Xen are buggy. For instance, I found that when you have two IPs with different subnets configured for Dom0 the DomUs won't be able to get an IP from your normal DHCP server. (Compare discussion on this list quite some time back.) I didn't see a problem with the network of the Dom0, though. Check dmesg and other logs for any bootup errors. Make sure that your network setup on the machine is 100% correct and all subnets have a dedicated gateway. Something that isn't 100% correct, but normally works, may not work with these network scripts. I went to Xen 3.2 which has a completely revamped network/bridging structure. Kai -- Kai Sch?tzl, Berlin, Germany Get your web at Conactive Internet Services: http://www.conactive.com