[Lxc-users] seeing a network pause when starting and stopping LXCs - how do I stop this ?

[Jäkel, Guido]

Dear Michael,

>I always hate replying to my own posts but I have stumbled onto some
>interesting clarification as I've continued to play with this...
>
>Below in-line.
> [...]

Again a well-done investigation. For everyone who don't have the time to carefully read this threads, i want to sum the (imho) key statements:


* With kernel 2.6.27ff, one MAY make a MAC sticky to a bridge using standard tools, e.g.

	ifconfig br0 hw ether "12:34:56:78:90:ab"

  This will turn off the "auto-select-the-lowest-MAC"-algorithm.



* But the MAC MUST be one of the attached NICs to get the stacks layer2 packet routing working.

  >The problem is that the bridge only thinks a packet is "local" if it arrives with destination hw addr == incoming device address.

  You might have more than one bridge and they may attached to different groups of NICs. Therefore, there have to be a layer 2 instrument (the MAC) to find the right bridge by its "table of MACs" spanned by the attached interfaces.



For us LXC-users it means, we should make the MAC of the hosts interface sticky to the attached bridge. Unfortunately, there's no support by the  brctrl   command for it (, like  'brctrl addif <bridge> <interface> [--sticky]'). Therefore, one have to use something like


	ifconfig $BRIDGE hw ether `LANG="" ifconfig $HOSTNIC | sed -ne "/HWaddr/ s/.* HWaddr \(.*\)$/\1/p"`

in an "ifup-post"-script.

greetings

Guido


-- 
Dr. Guido Jäkel
Deutsche Nationalbibliothek
IT SG 2.2 (Infrastruktur Unix)
Adickesallee 1
60322 Frankfurt am Main
Tel. +49-69-1525-1750
Fax  +49-69-1525-1799
mailto:g.jaekel at dnb.de
http://www.dnb.de