I've been running xen 4.2 on Fedora 19 for the last year or so. I've just switched to xen 4.4 on Debian Jessie and I simply cannot get even the most basic of networking to function. As far as I can tell, I have replicated the setup I had on Fedora (adjusting for the different conf file formats on Debian). My arrangement is simple: NIC1 and NIC2 are bonded, then attached to a bridge which in turn provides external internet access for the physical machine and certain of the VMs. There are then a series of subnets for different groupings of VMs which use internal only virtual bridges. In short then: br0 = external access; xenbr0, xenbr1, xenbr2 run subnets 10.0.0.x, 10.1.1.x, 10.2.2.x etc. My server has access to a block of /27 IPs. The server's IP is x.x.x.1 I try to set up a new Wheezy VM with an external IP with the following simple script: kernel="vmlinuz" ramdisk="initrd.gz" name = [x] maxmem = [x] memory = [x] vcpus = 1 disk = [ "phy:/dev/lvm/vm,xvda,w" ] vif = [ "mac=xx.xx.xx.xx.xx.xx,bridge=br0" ] During the setup I interrupt the dhcp process to assign a static address from my server's IP block. For example I will give the VM x.x.x.2/27, enter the correct gateway that the physical server is using and a working nameserver. After that nada! The link on eth0 is not detected, external mirrors are uncontactable etc. Am I missing something absurdly simple as this worked just fine before on Fedora? Is there some transitional detail I've missed from Fedora to Debian? I've been through all the networking pages on the wiki, tried adding -I FORWARD -m physdev --physdev-is-bridged -j ACCEPT to iptables, disabling netfilter on bridges in sysctl.conf etc. I'd really appreciate a fresh mind/pair of eyes that has any input to provide. Thanks.