Re: [Xen-users] bonding + vlans ALMOST working, NO ARP

[Tomasz Chmielewski <mangoo@xxxxxxxx>]

Eli Criffield wrote:
> I'm very close to getting bonding + vlans + bridging to work.
>
> The only part that's not working is ARP.
>
> Why i have no idea? But if put in an arp entry for the default route
> manually with 'arp -s 192.168.129.1 00:00:0C:07:0C:C9' everything
> works great.  (Everything that goes though the default route anyway).
>
> Now if i run tcpdump on any of the interfaces involved in the bridge,
> eth0, eth1, bond0, vlan151 or vlan151-br, vif0,0, or veth0 (i don't
> rename any interfaces) then it works fine, I get arp replays. But if i
> use 'ip' to turn on promisc any of the interfaces it doesn't work,
> just like it doesn't work without promisc off.
>
> The script is a little diffrent then the last one i posted, I'll atach
> it at the end.
>
> Basically I'm combining eth0 and eth1 into bond0, add vlans to bond0
> named "vlanXXX"  make a bridge named vlanXXX-br and add vlanXXX to it,
> and then domU's are started with bridge=vlanXXX-br in there xen config
> file to decide what vlan they should be part of.
>
> So what is tcpdump doing to make arp work???
Doesn't it look like this issue:

http://wiki.xensource.com/xenwiki/XenFaq#head-2e2a099d5575bb46de6d52786f093c13599af333

3.3. Why does my new domain receive no network traffic until after it 
initiates an outgoing connection?
This is an issue that occurs under the following circumstances:

    * You do not specify the domain's MAC address, causing a random MAC 
address to be selected at domain creation time
    * The upstream router has a local ARP cache

When a domain is destroyed, the host system's ARP cache is purged of 
addresses for the defunct virtual NIC. If the domain is recreated it is 
likely to be allocated a different random MAC address. This is no 
problem for the host machine, but the external switch/router still knows 
the "old" MAC address. The switch/router requires an outbound packet to 
the outside world to implicitly eradicate the old ARP-cache entry. This 
is not really Xen's fault at all, just a property of the implementation 
of ARP resolution.
--
Tomasz Chmielewski
http://wpkg.org

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