agr(4) + bridge(4): problems!

[Hugo Silva <hugo%barafranca.com@localhost>]

Recently I was troubleshooting network issues with a new NetBSD 6.0/Xen 
4.1 installation. The symptoms were that the domU was unable to resolve 
any names, or ping any host on the LAN (by IP address)

Further troubleshooting revealed that not even ARP was working.



On the host system, ifconfig.agr0 looks like:

create
link1
agrport wm1
agrport wm4
up
inet xxx.xxx.xxx.xxx netmask 255.255.255.0


Notice the link1 flag, which according to the manpage

"
     link1   Disable LACP.  Prevents any LACP or Marker messaging which 
leaves
             the ports in the default static configuration.  Set this 
prior to
             adding ports.
"


I ran some tests and with the link1 flag, downing one agrport would 
indeed not murder my ssh connection to the dom0. So everything appeared 
to be working fine, until I got to the VM network configuration stage.



An interesting symptom is that when a NetBSD PV domU is booting up, the 
ipv6 code detects a duplicate on the network (itself), while on the host 
brconfig output, the VM MAC appears twice.

I am wondering whether this should be expected or not. I suspect it's a bug?


I also wonder whether it's related to the use of the link1 flag. 
Presently I still don't have the new switches, where I do plan to setup 
lacp correctly. But that wouldn't solve the problem entirely as there 
will be other machines connected to other switches which do not and 
won't have any lacp configured.



I guess I could fall back to not using agr, but having the extra nics it 
would be cool to set it up like this!


Regards,

Hugo