[Fedora-xen] xen 3.1 network

Hello, i'd like to understand more deeply xen networking. My purpose is to modify the dscp ip field in guest's packet, to perform Qos, thanks to iptables. I'm using a FC7 with xen 3.1. I've installed a windows guest, with virt-manager, and I have used the default nat network option. Unfortunatelly, i couldn't use the bridge option because no network card was proposed! but this isn't the subject... I was quite surprised when i saw, in my xen-config.sxp : (network-script : network-bridge). it should be network-nat, am I wrong? the ifconfig command displays : lo Link encap:Boucle locale inet adr:127.0.0.1 Masque:255.0.0.0 adr inet6: ::1/128 Scope:Hôte UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:731062 errors:0 dropped:0 overruns:0 frame:0 TX packets:731062 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 lg file transmission:0 RX bytes:7695075004 (7.1 GiB) TX bytes:7695075004 (7.1 GiB) tap0 Link encap:Ethernet HWaddr 82:E3:26:59:DC:BF adr inet6: fe80::80e3:26ff:fe59:dcbf/64 Scope:Lien UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:17783 errors:0 dropped:0 overruns:0 frame:0 TX packets:513 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 lg file transmission:500 RX bytes:24458454 (23.3 MiB) TX bytes:181392 (177.1 KiB) tmpbridge Link encap:Ethernet HWaddr 00:00:00:00:00:00 inet adr:192.168.1.5 Bcast:192.168.1.255 Masque:255.255.255.0 adr inet6: fe80::200:ff:fe00:0/64 Scope:Lien UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:34 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 lg file transmission:0 RX bytes:0 (0.0 b) TX bytes:9046 (8.8 KiB) vif11.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF UP BROADCAST MULTICAST 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 lg file transmission:32 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) virbr0 Link encap:Ethernet HWaddr 82:E3:26:59:DC:BF inet adr:192.168.122.1 Bcast:192.168.122.255 Masque: 255.255.255.0 adr inet6: fe80::200:ff:fe00:0/64 Scope:Lien UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:21958 errors:0 dropped:0 overruns:0 frame:0 TX packets:1377 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 lg file transmission:0 RX bytes:24771762 (23.6 MiB) TX bytes:304511 (297.3 KiB) the "network-bridge status" displays : ============================================================ 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: peth0: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast qlen 1000 link/ether 00:08:02:f5:71:e6 brd ff:ff:ff:ff:ff:ff 3: virbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue link/ether 82:e3:26:59:dc:bf brd ff:ff:ff:ff:ff:ff inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0 inet6 fe80::200:ff:fe00:0/64 scope link valid_lft forever preferred_lft forever 4: tmpbridge: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff inet 192.168.1.5/24 brd 192.168.1.255 scope global tmpbridge inet6 fe80::200:ff:fe00:0/64 scope link valid_lft forever preferred_lft forever 21: vif11.0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 32 link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff 22: tap0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 500 link/ether 82:e3:26:59:dc:bf brd ff:ff:ff:ff:ff:ff inet6 fe80::80e3:26ff:fe59:dcbf/64 scope link valid_lft forever preferred_lft forever it seems like the network-bridge scripts crashes, because the tmpbridge is not renamed, and when I start the xend service or when I run network-bridge start, the eth0 interface is disable!! can anyone helps me debug this situation? thanks