Re: [Qemu-discuss] Bridging not working across qemu guests.

[Vlad Yasevich]

On 05/08/2015 04:46 AM, dE wrote:
> Hi!
> 
> I'm trying to get 2 qemu guest to connect via bridging. This is what I'm 
> doing --
> 
> modprobe tun;ip tuntap add mode tap veth;ip a add fc00::1001/124 dev veth;ip 
> link set dev
> veth up
> 
> qemu-system-x86_64 -machine accel=kvm,kernel_irqchip=on,mem-merge=on -drive
> file=centos7.qcow,id=centos,if=ide,media=disk,cache=unsafe,aio=native,index=0 
> -vnc :2
> -no-acpi -device e1000,id=ethnet,vlan=0 -net
> tap,ifname=veth,script=no,downscript=no,vlan=0 -m 512
> 
> modprobe tun;ip tuntap add mode tap veth0;ip a add fc00::1003/124 dev 
> veth0;ip link set
> dev veth0 up
> 
> qemu-system-x86_64 -machine accel=kvm,kernel_irqchip=on,mem-merge=on -drive
> file=centos7_2.qcow,id=centos,if=ide,media=disk,cache=unsafe,aio=native,index=0
>  -vnc :2
> -no-acpi -device e1000,id=ethnet,vlan=0 -net
> tap,ifname=veth0,script=no,downscript=no,vlan=0 -m 512
> ensure to change default IP in VM2.
> 
> ip a del fc00::1003/124 dev veth0
> ip a del fc00::1001/124 dev veth
> ip link set dev veth down
> ip link set dev veth0 down
> brctl addbr br
> brctl stp br off
> brctl addif br veth veth0

You've added veth0 to the bridge, but not veth.  Is this just a typo?  If not, 
that
would explain why VMs can't talk to each other.

-vlad

> ip link set dev veth up
> ip link set dev veth0 up
> ip link set promisc on dev veth0
> ip link set promisc on dev veth
> ip link set dev br up
> ip a add fc00::1001/124 dev br
> 
> The host can connect to both the VMs, and the VMs can ping it back, BUT the 
> VMs cannot
> connect to each other. They claim "destination unreachable"; that means 
> routes are present.
> 
> I've tried with both CentOS and system rescue CD.
> 
> Thanks or any help.
>