Networking proves elusive with Qemu

[Bob Bernstein <poobah%ruptured-duck.com@localhost>]

Prior to turning to virtualbox I had partial success with Qemu. 
With Qemu, my *bsd guests' VM's would complete successful boots 
on this Debian stable host, but the networking never worked.

There seemed to be a problem with routing, as the nic got its IP 
address and netmask and broadcast numbers. Pings seemed to send 
packets to remote hosts but never got any back. Pinging 
localhost worked ok.

Then I came across this statement in the Debian Qemu wiki:

"By default, QEMU invokes the -nic and -user options to add a 
single network adapter to the guest and provide NATed external 
Internet access."

My experience is that this does *not* happen here. I never get 
the NAT. So, for example, this command-line produces a quite 
workable NetBSD VM, but once it boots it has no network access:

# qemu-system-x86_64 -net nic -net user m=256 -cdrom 
boot-NetBSD-amd-7.0_RC3.iso nbsd.img

Anybody know what's lacking there?

* * *

nb. If anyone is curious why I am killing myself to get 
virtualization working on this box, the answer is here:

http://gnats.netbsd.org/47513

The machine in question, HP dc5850 desktop, is the one I gave 
Staples $99 for a refurb, with the express intention of 
installing NetBSD on it. No, I was not smart enough to check for 
bugs! It installs Debian no problem but in about one week I came 
to really really detest what they've done to linux under the 
guise of "systemd". (My Debian Jessie is running sans that 
monstrosity.)

Thank you again for your patience!

--
Bob Bernstein