Re: qemu guest with tap network not working

[Brook Milligan <brook%biology.nmsu.edu@localhost>]

> On Jul 2, 2025, at 16:03, Michael van Elst <mlelstv%serpens.de@localhost> wrote:
> 
> On Wed, Jul 02, 2025 at 03:17:42PM -0600, Brook Milligan wrote:
>> 
> 
>> The key is that the host needs an address on the bridge in the guest?s subnet so it can route packets.
> 
> When you add the host ethernet interface to the bridge, you do not route
> packets and you do not have a "guest subnet". It's all one, just like
> connecting the guest to the same switch the host is connected to.

That is what I thought, but for some reason it didn’t work earlier.

I’ve tried it again with a guest IP address within the subnet of the host’s network and a gateway equal to the host’s gateway.  That works, as you say.

Now this is making more sense to me, as it agrees with my expectations for how the bridged network should work.  I’m not sure where I went off the rails.

>> I?m not sure what ?neither? refers to.  In my experience testing this, some interface attached to the bridge (either tap or vether) needs an IP address for routing.
> 
> Connecting to the bridge connects the interfaces on layer 2, routing
> is not part of this and not required. Also, for connectivity to the
> outside, a routed guest network also needs proper routes on the host
> network. You can do that, but it adds lots of complexity.

Yes, which was why I went in that direction only because I had convinced myself (incorrectly as it turns out) that the other wasn’t working.

Thanks for your help.

Cheers,
Brook