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My setup is about as basic as you can get. I have 2 interfaces on dom0 (Debian Squeeze), eth0 and eth1. I created a bridge for eth1 to forward packets to domU that has a public IP address. I can connect (ssh) to dom0 over externally, but I can't get to domU externally. I'm trying to configure most of the network stack myself, so the only thing enabled in xend-config.sxp is (vif-script vif-bridge). What am I missing?

Assume x.y.z is the prefix to my public IPs.

dom0> /etc/xen/domU.cfg

vif = [ 'ip=x.y.z.243,mac=00:16:3E:AB:AE:DB,bridge=xenbr0' ]

dom0> /etc/network/interfaces

auto eth0
iface eth0 inet static
        address x.y.z.244
        netmask 255.255.255.248
        network x.y.z.240
        broadcast x.y.z.247
        gateway x.y.z.246
        dns-nameservers 8.8.8.8 8.8.4.4

allow-hotplug eth1
auto eth1
iface eth1 inet manual
        pre-up    /sbin/ifconfig eth1 up
        post-down /sbin/ifconfig eth1 down

auto xenbr0
iface xenbr0 inet manual
        bridge_ports eth1
        bridge_stp off
        bridge_maxwait 0
        bridge_fd 0

domU> /etc/network/interfaces

auto eth0
iface eth0 inet static
    address x.y.z.243
    netmask 255.255.255.248
    network x.y.z.240
    broadcast x.y.z.247
    gateway x.y.z.244

dom0> brctl show

bridge name bridge id       STP enabled interfaces
xenbr0      8000.002590a39820       no              eth1
                                                    vif4.0

dom0> ifconfig

eth0      Link encap:Ethernet  HWaddr 00:24:90:b3:78:21
          inet addr:x.y.z.244  Bcast:x.y.z.247  Mask:255.255.255.248
          inet6 addr: fe80::225:90ff:fea3:9821/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:40109 errors:0 dropped:0 overruns:0 frame:0
          TX packets:41103 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:4139025 (3.9 MiB)  TX bytes:6987850 (6.6 MiB)
          Interrupt:20 Memory:dfa00000-dfa20000

eth1      Link encap:Ethernet  HWaddr 00:25:90:a3:98:20
          inet6 addr: fe80::225:90ff:fea3:9820/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:220096 errors:0 dropped:0 overruns:0 frame:0
          TX packets:231831 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:23492354 (22.4 MiB)  TX bytes:41985393 (40.0 MiB)
          Interrupt:16 Memory:df900000-df920000

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:12 errors:0 dropped:0 overruns:0 frame:0
          TX packets:12 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:888 (888.0 B)  TX bytes:888 (888.0 B)

vif4.0    Link encap:Ethernet  HWaddr fe:ff:ff:ff:ff:ff
          inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link
          UP BROADCAST RUNNING PROMISC MULTICAST  MTU:1500  Metric:1
          RX packets:6 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4 errors:0 dropped:2 overruns:0 carrier:0
          collisions:0 txqueuelen:32
          RX bytes:384 (384.0 B)  TX bytes:300 (300.0 B)

xenbr0    Link encap:Ethernet  HWaddr 00:25:90:a3:98:20
          inet6 addr: fe80::225:90ff:fea3:9820/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:602 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:42751 (41.7 KiB)  TX bytes:552 (552.0 B)
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1 Answer

Two things. I usually put the IP address on the bridge. Also, I don't use the xend config file for this scenario.

See an example here: (you can modify it to use eth1)

http://wiki.xen.org/wiki/Network_Configuration_Examples_(Xen_4.1%2B)#Example_Debian-style_bridge_configuration_.28e.g._Debian.2C_Ubuntu.29

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I never really understood what putting an IP address on a bridge means; plus, this is just 1 VM of many that will be connected to the bridge, so I want to make sure the same bridge can be used for other domUs with public static IPs, AND I don't want packets with x.y.z.245 to be transferred over the bridge, but hit the eth0 interface instead. –  joshm1 Aug 19 '13 at 22:50
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