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

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] bonding + vlans ALMOST working, NO ARP
From: "Eli Criffield" <elicriffield@xxxxxxxxx>
Date: Fri, 1 Sep 2006 12:46:23 -0500
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I opened a bug for this issue

On 9/1/06, Eli Criffield <elicriffield@xxxxxxxxx> wrote:
Nea all mac's are set static so the switchs and routers with arp cache
don't have to update anything.


On 9/1/06, Tomasz Chmielewski <mangoo@xxxxxxxx> wrote:
> 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 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:
> 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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