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



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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