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Re: [Xen-users] bonding + VLANs -> Oops/panic, no VLAN on 100 Mbit cards

To: "Fajar A. Nugraha" <fajar@xxxxxxxxxxxxx>
Subject: Re: [Xen-users] bonding + VLANs -> Oops/panic, no VLAN on 100 Mbit cards [SOLVED]
From: Tomasz Chmielewski <mangoo@xxxxxxxx>
Date: Fri, 25 May 2007 14:02:14 +0200
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Fajar A. Nugraha schrieb:

(...)

Also you wrote it earlier ("I doubt it would work as expected anyway,
since the only way to get bonding and vlan in domU is to detect line
status (which would be rather useless if the network problem happens
anywhere other than the switch)") - so I'm not sure what you mean.



I believe it all comes down to your this line :
I doubt it would work as expected anyway, since the only way to get
bonding and vlan in *dom0* is to detect line status (which would be rather
useless if the network problem happens anywhere other than the switch)

I made a typo earlier, it should be dom0, not domU. The reasoning behind
that statement is :
1. there are several method that linux ethernet bonding use for link
monitoring, ARP monitor and the MII monitor
2. The best HA setup (IMHO) would be to use ARP monitor, and use router
IP as arp target.
3. Using vlans means multiple networks and multiple routers are involved.
4. Checking only one router ARP (the router on native-vlan) isn't really
good enough (for me anyway) since it doesn't check the conditions of
routers on other VLANs
5. MII monitor only check whether the link (the switch or hub that your
eth is connected to) is up. It doesn't really check whether the switch
connection to the router is working properly or not.

Which is why, IMHO, the best way to do bonding is in domU, and use dom0
for VLAN and bridge.
If you ever get a solution that would RELIABLY do bonding (as in capable
of checking each VLAN's router ARP) in dom0, I'd love to hear about it :)

Well, with my current setup, bonding works on dom0.
As it appears,only "sort of" - I have two issues at least:

1) I have about 1-2% packet losses - without bonding, I don't have such losses at all

2) when I try to do "arping <some_host>" from a Xen host, that host completely looses network connectivity (domains using VLANs don't loose the connectivity, though). A workaround is to use "arping -i bond0 <some_host>" - which is pretty strange, as hosts without Xen don't loose network connectivity in such case (yes, I understand that arping defaults to eth0 - but nevertheless, the host shouldn't loose network connectivity because of that).



Somehow, I don't like the way Xen messes with networking - as you said, I agree it's not that reliable :(


--
Tomasz Chmielewski
http://wpkg.org

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