# kernel config for qemu-kvm

## difficultcho

Hi,

I updated my kernel from 3.5.7 to 3.9.7 lately. It seems I messed up my virtual network configuration.

I am using libvirt and virt-manager with qemu-kvm, and want to setup my virtual network in the NAT mode.

In a terminal, if I type:

```
virsh net-start default
```

it returns:

```
error: Failed to start network default

error: failed to add iptables rule to block outbound traffic from 'virbr0'
```

trying to start from virt-manager will get similar error as "network default is not active"

the drivers are compiled as kernel modules, and here is my lsmod results:

 *Quote:*   

> 
> 
> Module                  Size  Used by
> 
> mmc_block            24767  0 
> ...

 

Also, if I try to add an outbound rule to my iptables by

```

iptables -A OUTPUT -p tcp --dport 22 -j DROP

```

It seems working to me.

So, may I ask what module am I missing in my kernel config? Thanks!

----------

## difficultcho

I tried some brute force method, which means to enable all options, and see if libvirt may start. And then reduce options gradually.

It turns out that:

networking support -->

    networking options -->

        network package filtering framework -->

            netfilter configuration -->

                packet filtering

                    REJECT target support

is the one I missed. It has a (NEW) marked on it, so I thought it wasn't a critical option.

----------

