[clug] Network bridges behind wireless ethernet bridges

Edward C. Lang edlang at edlang.org
Sat Dec 17 05:24:59 MST 2011


On 17/12/2011 18:08, Dale Shaw wrote:
> On Sat, Dec 17, 2011 at 5:31 PM, Edward C. Lang<edlang at edlang.org>  wrote:
>> I'm a little puzzled by a problem I've run into this afternoon in the
>> process of setting up some a new computer and some virtual servers.
> [... stuff ...]
> The topology seems simple enough at a bridging level.
> Definitely sounds like a MAC learning problem. Possibly some kind of
> ARP timer/MAC learning interaction.
> Does the connectivity only drop after a period of inactivity? When
> connectivity drops, is it only to the KVM host? That seems to be what
> you're saying.

Yup. For console SSH, I'd see "Write failed: Broken pipe". Other 
applications (virt-manager, deluge) would just lose their connection, 
generally at the most inopportune times! There was nothing in any log 
files that corresponded with these connection failures.

> What kind of device is the wireless bridge?

  * Asus RT-N12 running shibby's tomatousb build as the main AP
  * Asus RT-N16 running shibby's tomatousb build as the wireless bridge
  * KVM host is an HP Microserver running Ubuntu Oneiric with the most 
recent server kernel / libvirt packages / qemu packages

Contents of /etc/network/interfaces:

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet manual

# bridge device
auto br0
iface br0 inet dhcp
   bridge_ports eth0
   bridge_stp on
   bridge_maxwait 0

I suffered the same problems with both static and DHCP IP address 
assignment. The Ubuntu KVM and primary KVM documentation differs on 
enabling or disabling spanning tree protocol; neither fixed the problem. 
I also tried putting a bonded interface in between the physical and 
bridged interfaces.

Gus: the wireless bridge is very stable for other devices on it (PS3, 
WDTV Live Hub, an old laptop). The bridge was also very stable before I 
started virtualising the HP Microserver.  I've pushed several hundred 
gigabytes across it in the last month without issue, generally within 
speeds acceptable for 802.11n networks. I had to swap the roles of the 
RT-N12 and the RT-N16 as the opposite combination was extremely 
unstable... the RT-N12 kept locking up.

I'll try capturing some packets tomorrow.



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