I'm running KVM under CentOS 6. I created a VM, using a bridge network, and the guest and host are unable to communicate with each other. The guest and host can talk to everything else on the network fine, so I'm sure the issue is related to the network/bridge setup on the CentOS host.

On the KVM host, I have these interfaces:

eth0 (10.1.1.1)
macvtap0 (no IP)
virbr0 (192.168.1.1)

# brctl show
bridge name bridge id STP enabled interfaces
virbr0 8000.525400336713 yes virbr0-nic

The guest VM is setup with this networking:

Source device: Host device eth0: macvtap
Device model: Hypervisor default
Source mode: Bridge

The guest VM gets an IP address from the network, and it can access the Internet and everything else on the LAN. But it's unable to communicate with the CentOS host.

I assume there's more tweaking necessary on the CentOS host?

Thanks!

Greetingz!

First thing I always check are my iptables rules. If you feel safe doing so, you might want to temporarily stop the iptables / ip6tables service and give it another shot.

Yeah, I disabled iptables already and it didn't make any difference. I think the issue stems around the fact the VM guest is coming through my eth0 interface, which isn't bridged. I tried bridging eth0 through a br0 interface with no luck, but I'm going to try to find some good documentation and give it a try again.

This is how this should work:

eth0 (no IP) -> bridge (host IP goes here) <- VMs

No macvtaps, and the host's IP should be set up in the bridge's ifcfg, not the eth under the bridge

Bingo! I'm golden now. Thanks for the help!

Found this forum by googling the same problem.

I also have a Centos 6.2 machine with a virtual machine that cannot reach the host it's running on.
Although the information the in posts above is logical, I cannot convert them to commands/configuration files to make this work.

Could someone please post commands and/or config file or instructions on how to fix this?

Thanks

post your current set of config files, and we'll be able to suggest a fix

http://www.cyberciti.biz/faq/rhel-li...-with-libvirt/

Setup your br0 (bridge) interface using the above instructions to get you started. Ignore the eth1, br1 and custom routes which you probably don't need. Then you point your VMs to the "br0" host interface and all should work.

Thanks,

That will give me enough clues to get it fixed.