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Re: [Xen-users] Multiple Network Cards + Multiple Bridges on debian lenn

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Subject: Re: [Xen-users] Multiple Network Cards + Multiple Bridges on debian lenny
From: Alexander Pirsig <alex@xxxxxxxxxx>
Date: Mon, 31 Aug 2009 08:23:26 +0200
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Hi Max,

thank you for you answer. Okay maybe I have to give more information about my problem with bridge setup. Let me describe my server setup first.

I have a server with 4 network cards eth0-eth3. Network interfaces eth1-eth3 should be bridged and connected with xen domUs. At the moment my /etc/network/interfaces on Dom0 looks like this:

# The primary network interface
auto eth0
iface eth0 inet static

# eth1 -> intern 1
auto eth1
iface eth1 inet static
       up ifconfig eth1 up

# eth1 -> xenbr1
auto xenbr1
iface xenbr1 inet manual
       bridge_ports eth1
       down ifconfig xenbr1 down
       post-down brctl delbr xenbr1

# eth2 -> intern 2
auto eth1
iface eth1 inet static
       up ifconfig eth1 up

# eth2 -> xenbr2
auto xenbr2
iface xenbr2 inet manual
       bridge_ports eth2
       down ifconfig xenbr2 down
       post-down brctl delbr xenbr2

and so on.... in my /etc/xen/xend-config.sxp I have the following entries

(network-script network-dummy)
# (vif-script vif-bridge)

Then I configured networking for my DomU's like this:

#  Networking
vif  = [ 'ip=,bridge=xenbr1' ]

Bridge config on Dom0 looks like this:

xenbr1          8000.001b213b8a69       no              eth1
xenbr2          8000.001b213b8a6c       no              eth2
xenbr3          8000.001b213b8a6d       no              eth3

Yesterday I discovered that sometimes during Highload on DomU's part of the network is hard rechable with ssh or connections stalls even if I try to connect to dom0 with has seperate uplink.

checking arp sometimes shows strange information (during highload) like:

arp -na
? ( at 00:1b:21:3b:8a:68 [ether] on eth0
? ( at 00:1b:21:3b:8a:68[ether] on xenbr1

So my question are:

1. Is it normal that bridge xenbr1 claims ip mac address of eth1?
2. Do I have to reset mac address on the bridge (xenbr1) or network interface (eth1) to FF:FF:FF:FF bevor starting it.
3. What could cause the problem with the arp table?
4. Do I have to turn of  arp/multicast on eth1 or xenbr1 like this ->
   ip link set xenbr1 arp off
   ip link set xenbr1 multicast off



Maximilian Wilhelm wrote:
Anno domini 2009 Alexander Pirsig scripsit:


I'm searching for a tutorial how to setup multiple network cards with
xen network bridge setup in debian lenny. My problem is, bridges seams
only to work if i put an ip adress in dom0 to them.

Can you be a bit more specific about your problem?

When you have install the bridge-utils package, which is required for
configuring bridges on Debian, you can put stanzas like this into the
/etc/network/interfaces file:

auto br123
iface br123 inet manual
        bridge_ports eth42
        bridge_stp no
        bridge_fd 2

This will setup the bridge 'br123' and attach the physical NIC 'eth42'
to it, which practically means you have a virtual switch inside your
Dom0 where you can plug DomUs in. Dom0 will not be able to directly
communicate with them, though.

If you want your Dom0 to be part of this network, you have to
configure an IP address on the bridge which can be done like this:

auto br123
iface br123 inet static
        bridge_ports eth42
        bridge_stp no
        bridge_fd 2

Beware of the 'static' vs. 'manual' thing.

If you are using VLANs you can go one step further an do something
like this (package vlan required)

auto eth0
iface eth0 inet manual
        post-up ifconfig eth0 up
        pre-down ifconfig eth0 down

auto eth0.123
iface eth0.123 inet manual
        vlan_raw_device eth0
        post-up ifconfig $IFACE up
        pre-down ifconfig $IFACE down

auto br123
iface br123 inet static
        bridge_ports eth0.123
        bridge_stp no
        bridge_fd 2


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