Xen Networking: Difference between revisions

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(Improve the MAC address section)
(Overhaul briding section)
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In both cases the device naming is subject to the usual guest or backend domain facilities for renaming network devices. For the remainder of this document the default Linux naming, that is ''ethN'' for frontend and ''vifDOMID.DEVID'' for backend devices, will be used.
In both cases the device naming is subject to the usual guest or backend domain facilities for renaming network devices. For the remainder of this document the default Linux naming, that is ''ethN'' for frontend and ''vifDOMID.DEVID'' for backend devices, will be used.


The front and backend devices are linked by a virtual communication channel, guest networking is achieved by arranging for traffic to pass from the backend device onto the wider network, e.g. using bridge, routing or Network Address Translation (NAT).
The front and backend devices are linked by a virtual communication channel, guest networking is achieved by arranging for traffic to pass from the backend device onto the wider network, e.g. using bridging, routing or Network Address Translation (NAT).


= MAC addresses =
= MAC addresses =
Line 28: Line 28:


= Bridging =
= Bridging =
'''Illustration on network-bridge and vif-bridge:'''


The default (and most common) Xen configuration uses bridging within the backend domain (typically domain 0) to allow all domains to appear on the network as individual hosts.
http://koocotte.googlepages.com/Diapositive6.png


In this configuration a software bridge is created in the backend domain. The backend virtual network devices (''vifDOMID.DEVID'')) are added to this bridge along with an (optional) physical Ethernet device to provide connectivity off the host. By omitting the physical Ethernet device an isolated network containing only guest domains can be created.
The default Xen configuration uses bridging within domain 0 to allow all domains to appear on the network as individual hosts. If extensive use of iptables is made in domain 0 (e.g. a firewall) then this can affect bridging because bridged packets pass through the PREROUTING, FORWARD and POSTROUTING iptables chains. This means that packets being bridged between guest domains and the external network will need to be permitted to pass those chains. The most likely problem is the FORWARD chain being configured to DROP or REJECT packets (this is different from IP forwarding in the kernel).


There are two common naming schemes when using bridged networking. In one scheme the physical device ''eth0'' is renamed to ''peth0'' and a bridge named ''eth0'' is created. In the other the physical device remains ''eth0'' while the bridge is named ''xenbr0'' (or ''br0'' etc). We shall use the ''eth0''+''xenbr0'' naming scheme here.
iptable FORWARDing can be disabled for all packets; to prevent the dom0 from acting as an IP router: <code><nowiki>echo 0 > /proc/sys/net/ipv4/ip_forward</nowiki></code>.


Of course you are free to use whatever names you like, including descriptive names (e.g. "dmz", "internal", "external" etc).
A slightly more secure method is to allowing packet forwarding (at the iptables level) between the external physical interface and the vifs for the guests. For a machine with a single ethernet card this would be:


== Setting up bridged networking ==


The recommended method for configuring bridged networking is to use your distro supplied network configuration tools as described in [[Host Configuration/Networking]].
<pre>
iptables -A FORWARD -m physdev --physdev-in eth0 --physdev-out '!' eth0 -j ACCEPT
iptables -A FORWARD -m physdev --physdev-out eth0 --physdev-in '!' eth0 -j ACCEPT
</pre>


Prior to Xen 4.1 when xend started up it would run the <code>network-bridge</code> script which would reconfigure any existing physical network configuration into a bridged network configuration i.e. it would create a bridge, move the IP address from the physical device to the bridge, add the physical device to the bridge etc. However this was fragile and prone to breaking and therefore is no longer recommended.
(needs the ipt_physdev [aka xt_physdev] module to be available).


After Xen 4.1 xend will only do this if no bridges currently exist, so as to avoid overwriting any locally configured network configuration.
The ebtables project has an [http://ebtables.sourceforge.net/br_fw_ia/br_fw_ia.html interesting document on the interaction of bridging and iptables].


The [[XL]] toolstack will never modify the network configuration and expects that the administrator will have configured the host networking appropriately.
== Packet flow in bridging ==
([http://lists.xensource.com/archives/html/xen-users/2006-02/msg00586.html By Ernst Bachman])


== Attaching virtual devices to the appropriate bridge ==
Packet arrives at hardware, is handled by dom0 Ethernet driver and appears on <code><nowiki>peth0</nowiki></code>. <code><nowiki>peth0</nowiki></code> is bound to to the bridge, so its passed to the bridge from there. This step is run on Ethernet level, no IP addresses are set on <code><nowiki>peth0</nowiki></code> or bridge.


When a domU starts up the <code>vif-bridge</code> script is run which:
Now the bridge distributes the packet, just like a switch would. Filtering at this stage would be possible with [http://ebtables.sourceforge.net/ ebtables].


# attaches ''vifDOMID.DEVID'' to the appropriate bridge
Now there's a number of <code><nowiki>vifX.Y</nowiki></code> connected to the bridge, it decides where to put the packet based on the receiver's MAC.
# brings ''vifDOMID.DEVID'' up.


With [[XL]] and xend the bridge to us for each VIF can be configured using the ''bridge'' configuration key. e..g
The <code><nowiki>vif</nowiki></code> interface puts the packet into Xen, which then puts the packet back to the domain the <code><nowiki>vif</nowiki></code> leads to (its also done that way for dom0, hence the <code><nowiki>vif0.0</nowiki></code>-><code><nowiki>(v)eth0</nowiki></code> pair).
vif=[ 'bridge=mybridge' ]

or
The target device in the dom0/domU finally has an IP address, you can apply iptables filtering here.
vif=[ 'mac=00:16:3e:01:01:01,bridge=mybridge' ]

or to create multiple interfaces attached to different bridges:
== network-bridge ==
vif=[ 'mac=00:16:3e:70:01:01,bridge=br0', 'mac=00:16:3e:70:02:01,bridge=br1' ]
When xend starts up, it runs the <code><nowiki>network-bridge</nowiki></code> script, which:

# creates a new bridge named <code><nowiki>xenbr0</nowiki></code>
# "real" ethernet interface <code><nowiki>eth0</nowiki></code> is brought down
# the IP and MAC addresses of <code><nowiki>eth0</nowiki></code> are copied to virtual network interface <code><nowiki>veth0</nowiki></code>
# real interface <code><nowiki>eth0</nowiki></code> is renamed <code><nowiki>peth0</nowiki></code>
# virtual interface <code><nowiki>veth0</nowiki></code> is renamed <code><nowiki>eth0</nowiki></code>
# <code><nowiki>peth0</nowiki></code> and <code><nowiki>vif0.0</nowiki></code> are attached to bridge <code><nowiki>xenbr0. </nowiki></code>Please notice that in xen 3.3, the default bridge name is the same than the interface it is attached to. Eg: bridge name eth0, eth1 or ethX.VlanID
# the bridge, <code><nowiki>peth0</nowiki></code>, <code><nowiki>eth0</nowiki></code> and <code><nowiki>vif0.0</nowiki></code> are brought up
It is good to have the physical interface and the dom0 interface separated; thus you can e.g. setup a firewall on dom0 that does not affect the traffic to the domUs (just for protecting dom0 alone).

== vif-bridge ==
When a domU starts up, <code><nowiki>xend</nowiki></code> (running in dom0) runs the <code><nowiki>vif-bridge</nowiki></code> script, which:

# attaches <code><nowiki>vif<id#>.0</nowiki></code> to <code><nowiki>xenbr0</nowiki></code>
# <code><nowiki>vif<id#>.0</nowiki></code> is brought up
== Additional Notes ==
* you can change the bridge name from <code><nowiki>xenbr0</nowiki></code> using:
<pre>
(network-script 'network-bridge bridge=mybridge')
</pre>

in <code><nowiki>xend-config.sxp</nowiki></code> and rebooting or restarting <code><nowiki>xend</nowiki></code>
* remember to configure the bridge to attach to in the domU's config file using:
<pre>
vif=[ 'bridge=mybridge' ]
</pre>

or perhaps something like:
<pre>
vif=[ 'mac=00:16:3e:01:01:01,bridge=mybridge' ]
</pre>

* you can create multiple network interfaces, and attach them to different bridges using:
<pre>
vif=[ 'mac=00:16:3e:70:01:01,bridge=br0', 'mac=00:16:3e:70:02:01,bridge=br1' ]
</pre>

* if you want to use multiple bridges, you must create them yourself, either manually, or via your own startup script, or via a custom script to replace <code><nowiki>network-bridge</nowiki></code>. For example:
<pre>
$ cd /etc/xen/scripts
$ cp network-bridge network-custom
$ cp vif-bridge vif-custom
$ vi /etc/xen/xend-config.sxp
(network-script network-custom)
(vif-script vif-custom)
$ vi network-custom
# whatever you want
</pre>

* before you connect a physical interface to a bridge, remember to reset it's mac and turn arp off. For example:
<pre>
# ip link set eth1 down
# ip link set eth1 mac fe:ff:ff:ff:ff:ff arp off
# brctl addif br1 eth1
# ip link set eth1 up
</pre>

* With Xen 3.0 the best method for additional bridges is to use the default Xen scripts with a slight modification. Following the [http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=332 XenBug #332]. For example in a two bridge network with eth0 and eth1. Create /etc/xen/scripts/my-network-script with
<pre>
#!/bin/sh
dir=$(dirname "$0")
"$dir/network-bridge" "$@" vifnum=0
"$dir/network-bridge" "$@" vifnum=1
</pre>

* With Xen 3.2.1 (tested on Debian Etch 4.0r3), here is a script example that creates two virtual interfaces corresponding to the 2 physical network interfaces
<pre>
# xemacs /etc/xen/scripts/network-bridge-wrapper
#!/bin/sh
/etc/xen/scripts/network-bridge "$@" netdev=eth0
/etc/xen/scripts/network-bridge "$@" netdev=eth1
</pre>

The $1 will use the argument of xend (in the /etc/xen/xend-config.sxp configuration file). If there is a default physical network interface, the standard network-bridge script of Xen will create a vif for this interface, and not the other ones also.

* (Additional note by steve_from_moreover - May be stating the obvious but remember to do - chmod 755 /etc/xen/scripts/my-network-script or when you reboot it will silently not be able to run this script).
* On SuSE Linux (at least), each interface requires an ifcfg script in /etc/sysconfig/network, e.g. /etc/sysconfig/network/ifcfg-eth1. Otherwise, network-bridge will create the bridge with no interfaces attached.
* Then change /etc/xen/xend-config.sxp with the following (network-script my-network-script).
* The same principle can apply to networks without a physical ethernet device. Use a dummy interface with
<pre>
"$dir/network-bridge" "$@" vifnum=2 netdev=dummy0
</pre>


== Links ==
== Links ==
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* [http://lists.xensource.com/archives/html/xen-users/2006-03/msg00109.html Another way for making multiple Xen bridges]
* [http://lists.xensource.com/archives/html/xen-users/2006-03/msg00109.html Another way for making multiple Xen bridges]
* [http://lists.xensource.com/archives/html/xen-users/2007-05/msg00064.html Advanced bridging (2007/05)] You can also have a look to: http://searchservervirtualization.techtarget.com/tip/0,289483,sid94_gci1310165,00.html#
* [http://lists.xensource.com/archives/html/xen-users/2007-05/msg00064.html Advanced bridging (2007/05)] You can also have a look to: http://searchservervirtualization.techtarget.com/tip/0,289483,sid94_gci1310165,00.html#

= Routing =
= Routing =
This section applies only if you choose to use <code><nowiki>network-route</nowiki></code> and <code><nowiki>vif-route</nowiki></code> instead of <code><nowiki>network-bridge</nowiki></code> and <code><nowiki>vif-bridge</nowiki></code>.
This section applies only if you choose to use <code><nowiki>network-route</nowiki></code> and <code><nowiki>vif-route</nowiki></code> instead of <code><nowiki>network-bridge</nowiki></code> and <code><nowiki>vif-bridge</nowiki></code>.

Revision as of 16:04, 25 June 2012

Icon todo.png Needs Review

This page has been marked as out-of-date and needs review and its content needs to be updated for Xen 4.x.


Virtual Network Interfaces

When a domain is started with a network interface then the Xen toolstack will create a pair of network devices. The first of these (the frontend) will reside in the guest domain while the second (the backend) will reside in the backend domain (typically Dom0). A similar pair of devices is created for each virtual network interface

The frontend devices appear much like any other physical Ethernet NIC in the guest domain. Typically under Linux it is bound to the xen-netfront driver and creates a device ethN. Under NetBSD and FreeBSD the frontend devices are named xennetN and xnN respectively.

The backend device is typically named such that it contains both the guest domain ID and the index of the device. Under Linux such devices are by default named vifDOMID.DEVID while under NetBSD xvifDOMID.DEVID is used.

In both cases the device naming is subject to the usual guest or backend domain facilities for renaming network devices. For the remainder of this document the default Linux naming, that is ethN for frontend and vifDOMID.DEVID for backend devices, will be used.

The front and backend devices are linked by a virtual communication channel, guest networking is achieved by arranging for traffic to pass from the backend device onto the wider network, e.g. using bridging, routing or Network Address Translation (NAT).

MAC addresses

Virtualised network interfaces in domains are given Ethernet MAC addresses. By default most Xen toolstacks will select a random address, depending on the toolstack this will either be static for the entire life time of the guest (e.g. Libvirt, XAPI or xend managed domains) or will change each time the guest is started (e.g. XL or xend unmanaged domains).

In the latter case if a fixed MAC address is required e.g. for using with DHCP then this can be be configured using the mac= option to the vif configuration directive (e.g. vif = ['mac=aa:00:00:00:00:11']). See XL Network Configuration for more details of the syntax.

When choosing MAC addresses there are in general three strategies which can be used. In decreasing order of preference these are:

  • Assign an address from the range associated with an Organizationally Unique Identifier (OUI) which you control. If you do not know what this means then you likely do not control an OUI and this option does not apply to you.
  • Generate a random sequence of 6 bytes, set the locally administered bit (bit 2 of the first byte) and clear the multicast bit (bit 1 of the first byte). In other words the first byte should have the bit pattern xxxxxx10 (where x is a randomly generated bit) and the remaining 5 bytes are randomly generated. See wikipedia for more details the structure of a MAC address.
  • Assign a random address from within the space 00:16:3e:xx:xx:xx. 00:16:3e is an OUI assigned to the Xen project and which has been made available for Xen users for the purposes of assigning local addresses within that space.

A MAC address must be unique among all network devices (both physical and virtual) on the same local network segment (e.g. on the LAN containing the Xen host). For this reason if you do not have your own OUI to use it is in general recommended to generate a random locally administered address (the second option above) rather than using the Xen OUI (the third option) since it gives 46 bits of randomness rather than 12 which significantly reduces the chances of a clash.

Bridging

The default (and most common) Xen configuration uses bridging within the backend domain (typically domain 0) to allow all domains to appear on the network as individual hosts.

In this configuration a software bridge is created in the backend domain. The backend virtual network devices (vifDOMID.DEVID)) are added to this bridge along with an (optional) physical Ethernet device to provide connectivity off the host. By omitting the physical Ethernet device an isolated network containing only guest domains can be created.

There are two common naming schemes when using bridged networking. In one scheme the physical device eth0 is renamed to peth0 and a bridge named eth0 is created. In the other the physical device remains eth0 while the bridge is named xenbr0 (or br0 etc). We shall use the eth0+xenbr0 naming scheme here.

Of course you are free to use whatever names you like, including descriptive names (e.g. "dmz", "internal", "external" etc).

Setting up bridged networking

The recommended method for configuring bridged networking is to use your distro supplied network configuration tools as described in Host Configuration/Networking.

Prior to Xen 4.1 when xend started up it would run the network-bridge script which would reconfigure any existing physical network configuration into a bridged network configuration i.e. it would create a bridge, move the IP address from the physical device to the bridge, add the physical device to the bridge etc. However this was fragile and prone to breaking and therefore is no longer recommended.

After Xen 4.1 xend will only do this if no bridges currently exist, so as to avoid overwriting any locally configured network configuration.

The XL toolstack will never modify the network configuration and expects that the administrator will have configured the host networking appropriately.

Attaching virtual devices to the appropriate bridge

When a domU starts up the vif-bridge script is run which:

  1. attaches vifDOMID.DEVID to the appropriate bridge
  2. brings vifDOMID.DEVID up.

With XL and xend the bridge to us for each VIF can be configured using the bridge configuration key. e..g 

   vif=[ 'bridge=mybridge' ]

or 

   vif=[ 'mac=00:16:3e:01:01:01,bridge=mybridge' ]

or to create multiple interfaces attached to different bridges: 

   vif=[ 'mac=00:16:3e:70:01:01,bridge=br0', 'mac=00:16:3e:70:02:01,bridge=br1' ]

Links

Some relevant topics from the mailing list:

Routing

This section applies only if you choose to use network-route and vif-route instead of network-bridge and vif-bridge.

Illustration on network-route and vif-route:

pngri9SMxMw7l.png

Routing creates a point-to-point link between dom0 and each domU. Routes to each domU are added to dom0's routing table, so domU must have a known (static) IP. DHCP doesn't work, because the route won't be created, and the DHCP offer won't arrive.

network-route

When xend starts up, it runs network-route which:

  1. enables ip forwarding within dom0

vif-route

When domU starts up, xend runs (within dom0) vif-route which:

  1. copies the ip address from eth0 to vif<id#>.0
  2. brings up vif<id#>.0
  3. adds host static route for domU's ip address specified in domU config file, pointing at interface vif<id#>.

More information on vif-route can be found here: http://wiki.xensource.com/xenwiki/vif-route

Reference

Virtual Network

The virtual network is currently a non-standard configuration.

Illustration of virtual network setups:

Diapositive9.png

The virtual network configuration places all domU on a shared virtual network with dom0. This allows domU to use a DHCP server provided by dom0, without allowing DHCP requests from domU to escape onto the physical network. (As far as I can tell, vif0.0 and dummy0 are not strictly required.)

Links

Interface names

The default configuration for Xen systems is to use bridging. When xend starts it creates a bridge called xen-br0. xend takes the IP address etc. from eth0 and assigns to xen-br0 (as dom0's interface onto the bridge). So dom0's own external-facing interface is now xen-br0 - make sure any firewall config reflects this.

VLANs

1st method of having VMs using vlan interfaces with XEN.

Multiple tagged VLANs can be supported by configuring 802.1Q VLAN support into domain 0. A local interface in dom0 is needed for each desired VLAN although it need not have an IP address in dom0. A bridge can be set up for each VLAN, and guests can then connect the the appropriate bridge.

My (JamesBulpin) prefered method is to define the bridge as an interface which is not brought up automatically (e.g. for Debian /etc/network/interfaces, with no "auto" entry): 


iface xen-br293 inet manual
    up vconfig add eth0 293
    up /etc/xen/scripts/network start netdev=eth0.293 bridge=xen-br293 antispoof=no
    up /sbin/ifconfig eth0.293 up
    down /etc/xen/scripts/network stop netdev=eth0.293 bridge=xen-br293 antispoof=no
    down vconfig rem eth0.293

I then add an init.d script to bring the interface up between xend and xendomains starting.

2nd method for XEN with vlans: modify network-bridge script

I (OrianaPalivan) used this method because I needed to have a particular use (and quite general on my oppinion) of my VMs. Hope this may help you with your future VMs.

It was tested with xen 3.3, and Debian Etch 4.r05. Please notice that with xen 3.3, the name of the bridge is the name of the interface in the domain 0 it is attached to (so no xenbr anymore by default).

Domain 0 has 2 interfaces: eth0 and eth1, each of them has 2 vlan interfaces attached, for example eth0.20, eth0.21 and eth1.3916 and eth1.3999.

Here is the network configuration of the VMs:

  • VM1: eth0 -> domain 0, eth0 / eth1 -> domain 0, eth1
  • VM2: eth0 -> domain 0, eth0.20 / eth1 -> domain 0, eth1.3999
  • VM3: eth0 -> domain 0, eth0.21 / eth1 -> domain 0, eth1.3916
  • VM4: eth0 -> domain 0, eth0 / eth1 -> domain 0, eth1

I needed to be able to reach domain 0 thru IP.

Here are the steps for having all the interfaces from domain 0 (vlan or not vlan interface) ready to be used by the VMs:

  • Configure vlan interfaces (needs the vlan package)
  • Change the network-bridge script (located in /etc/xen/scripts)
    • Copy for example the network-bridge script to network-bridge-withvlan script
    • Edit the network-bridge-withvlan script. Comment each time ifup or ifdown commands are executed.The reason is that ifdown ends with error for vlan interfaces.

Change do_ifup() function: 


do_ifup() {
#    if ! ifup $1 ; then
   if [ -n "$addr_pfx" ] ; then
       # use the info from get_ip_info()
       ip addr flush $1
       ip addr add ${addr_pfx} dev $1
       ip link set dev $1 up
       [ -n "$gateway" ] && ip route add default via ${gateway}
   fi
   #fi
}

Change op_start() and op_stop() functions: 


op_start () {
[...]
#    if ! ifdown ${netdev}; then
      # If ifdown fails, remember the IP details.
    get_ip_info ${netdev}
    ip link set ${netdev} down
    ip addr flush ${netdev}
#    fi
op_stop () {
[...]
#    if ! ifdown ${bridge}; then
    get_ip_info ${bridge}
<!-- #    fi

-->
  • Create your network-bridge wrapper which will call the network-bridge-withvlan:
<16:39>[root:/etc/xen/scripts]# cat network-bridge-wrapper
#!/bin/sh
/etc/xen/scripts/network-bridge-withvlan "$@" netdev=eth0
/etc/xen/scripts/network-bridge-withvlan "$@" netdev=eth1
/etc/xen/scripts/network-bridge-withvlan "$@" netdev=eth0.20
/etc/xen/scripts/network-bridge-withvlan "$@" netdev=eth0.21
/etc/xen/scripts/network-bridge-withvlan "$@" netdev=eth1.3916
/etc/xen/scripts/network-bridge-withvlan "$@" netdev=eth1.3999#
  • Call your new network-bridge-wrapper in your xend-config.xsp
(network-script network-bridge-wrapper)
  • Before you restart your domain 0, do not forget to disable transmit checksum offloading (see below). You can make a script at startup:
<16:40>[root:/etc/xen]# cat /etc/init.d/xen-vlan
#!/bin/sh
ethtool -K eth0 tx off
ethtool -K eth1 tx off
  • At boot time, and before starting your VMs, make a :
 /etc/init.d/networking restart

In some cases, the static routes you have may not come up after xend starts.
  • In the configuration file of your VMs, you can now use the vlan interfaces:

VM1: 


vif = ['type=ioemu, mac=00:16:3E:00:00:13, bridge=eth0' , 'type=ioemu, mac=00:16:3E:00:00:14, bridge=eth1']

VM2: 


vif = ['type=ioemu, mac=00:16:3E:00:00:10, bridge=eth0.20' , 'type=ioemu, mac=00:16:3E:00:00:12, bridge=eth1.3999']

VM3: 


vif = ['type=ioemu, mac=00:16:3E:00:00:01, bridge=eth0.21' , 'type=ioemu, mac=00:16:3E:00:00:02, bridge=eth1.3916']

VM4: 


vif = ['type=ioemu, mac=00:16:3E:00:00:03, bridge=eth0' , 'type=ioemu, mac=00:16:3E:00:00:04, bridge=eth1']

Yet Another ASCII Graphics Description of Xen Networking

Xen 3.1- Networking

      LAN0                                                  LAN1
       |                                                     |
 +-----+-----------------------------------------------------+-----+
 |     |                                                     |     |
 | +---+-------------------------+ +-------------------------+---+ |
 | |   |                         | |                         |   | |
 | | peth0            xenbr0     | |      xenbr1           peth1 | |
 | |                             | |                             | |
 | | xenbr0       vif1.0  vif1.1 | |  vif2.0  vif2.1      xenbr1 | |
 | |                |       \    | |    /       |                | |
 | +---^------------+---------\--+ +--/---------+------------^---+ |
 |     |            |           \   /           |            |     |
 |     |     +------+-------------X-------------+------+     |     |
 |     |     |      |           /   \           |      |     |     |
 |     |     | +----+---------/--+ +--\---------+----+ |     |     |
 |     |     | |    |       /    | |    \       |    | |     |     |
 |     |     | |  eth0    eth1   | |   eth0   eth1   | |     |     |
 |     |     | |    |       |    | |    |       |    | |     |     |
 |   +-+-+   | |  +-+-+   +-+-+  | |  +-+-+   +-+-+  | |   +-+-+   |
 |   |   |   | |  |   |   |   |  | |  |   |   |   |  | |   |   |   |
 |  www ssh  | | www ssh ftp pop | | www ssh ftp pop | |  ftp pop  |
 |           | |                 | |                 | |           |
 |  Domain0  | |     Domain1     | |     Domain2     | |  Domain0  |
 +-----------+ +-----------------+ +-----------------+ +-----------+

Notes:

  • vif0.0 is absolute different from vif1.0. vif0.0 is created by netloop, while vif1.0 is created by netback.

Xen 3.2+ Networking

      LAN0                                                  LAN1
       |                                                     |
 +-----+-----------------------------------------------------+-----+
 |     |                                                     |     |
 | +---+-------------------------+ +-------------------------+---+ |
 | |   |                         | |                         |   | |
 | | peth0                       | |                       peth1 | |
 | |                             | |                             | |
 | | xenbr0       vif1.0  vif1.1 | |  vif2.0  vif2.1      xenbr1 | |
 | |                |       \    | |    /       |                | |
 | +---^------------+---------\--+ +--/---------+------------^---+ |
 |     |            |           \   /           |            |     |
 |     |     +------+-------------X-------------+------+     |     |
 |     |     |      |           /   \           |      |     |     |
 |     |     | +----+---------/--+ +--\---------+----+ |     |     |
 |     |     | |    |       /    | |    \       |    | |     |     |
 |     |     | |  eth0    eth1   | |   eth0   eth1   | |     |     |
 |     |     | |    |       |    | |    |       |    | |     |     |
 |   +-+-+   | |  +-+-+   +-+-+  | |  +-+-+   +-+-+  | |   +-+-+   |
 |   |   |   | |  |   |   |   |  | |  |   |   |   |  | |   |   |   |
 |  www ssh  | | www ssh ftp pop | | www ssh ftp pop | |  ftp pop  |
 |           | |                 | |                 | |           |
 |  Domain0  | |     Domain1     | |     Domain2     | |  Domain0  |
 +-----------+ +-----------------+ +-----------------+ +-----------+

Notes:

  • eth0 and eth1 are the bridge names, which is a bit confusing.

Alternative Xen Networking Architecture

      LAN0                                                  LAN1
       |                                                     |
 +-----+-----------------------------------------------------+-----+
 |     |                                                     |     |
 | +---+-------------------------+ +-------------------------+---+ |
 | |   |                         | |                         |   | |
 | | eth0                        | |                        eth1 | |
 | |                             | |                             | |
 | | xenbr0       vif1.0  vif1.1 | |  vif2.0  vif2.1      xenbr1 | |
 | |                |       \    | |    /       |                | |
 | +---^------------+---------\--+ +--/---------+------------^---+ |
 |     |            |           \   /           |            |     |
 |     |     +------+-------------X-------------+------+     |     |
 |     |     |      |           /   \           |      |     |     |
 |     |     | +----+---------/--+ +--\---------+----+ |     |     |
 |     |     | |    |       /    | |    \       |    | |     |     |
 |     |     | |  eth0    eth1   | |   eth0   eth1   | |     |     |
 |     |     | |    |       |    | |    |       |    | |     |     |
 |   +-+-+   | |  +-+-+   +-+-+  | |  +-+-+   +-+-+  | |   +-+-+   |
 |   |   |   | |  |   |   |   |  | |  |   |   |   |  | |   |   |   |
 |  www ssh  | | www ssh ftp pop | | www ssh ftp pop | |  ftp pop  |
 |           | |                 | |                 | |           |
 |  Domain0  | |     Domain1     | |     Domain2     | |  Domain0  |
 +-----------+ +-----------------+ +-----------------+ +-----------+

Notes:

  • based on xen 3.3, change bridge name to xenbr0, xenbr1, ...
  • xenbrX has an active address, which is used by dom0 to communicate with outside.

Xen Networking with vlan

      LAN0                                                  LAN1
       |                                                     |
 +-----+-----------------------------------------------------+-----+
 |     |                                                     |     |
 |   eth0                                                  eth1    |
 |     |                                                     |     |
 | +---+-------------------------+ +-------------------------+---+ |
 | |   |                         | |                         |   | |
 | | eth0.100                    | |                    eth1.200 | |
 | |                             | |                             | |
 | | xenbr0       vif1.0  vif1.1 | |  vif2.0  vif2.1      xenbr1 | |
 | |                |       \    | |    /       |                | |
 | +---^------------+---------\--+ +--/---------+------------^---+ |
 |     |            |           \   /           |            |     |
 |     |     +------+-------------X-------------+------+     |     |
 |     |     |      |           /   \           |      |     |     |
 |     |     | +----+---------/--+ +--\---------+----+ |     |     |
 |     |     | |    |       /    | |    \       |    | |     |     |
 |     |     | |  eth0    eth1   | |   eth0   eth1   | |     |     |
 |     |     | |    |       |    | |    |       |    | |     |     |
 |   +-+-+   | |  +-+-+   +-+-+  | |  +-+-+   +-+-+  | |   +-+-+   |
 |   |   |   | |  |   |   |   |  | |  |   |   |   |  | |   |   |   |
 |  www ssh  | | www ssh ftp pop | | www ssh ftp pop | |  ftp pop  |
 |           | |                 | |                 | |           |
 |  Domain0  | |     Domain1     | |     Domain2     | |  Domain0  |
 +-----------+ +-----------------+ +-----------------+ +-----------+

Notes:

  • With this configuration, DomUs are completely unaware of the fact that they are utilizing a VLAN, all the work is done within the bridges in Dom0.
  • Dom0 is aware of the traffic within the VLAN, because it has an active address on the xenbrX interfaces. To prevent it, don't give the xenbrX an active address, but configure a extra interface for management.
  • There are two things may need to be configured:
    • If your ethernet card does not natively support VLAN tags, you will have to set the maximum MTU to 1496 to make room for the tag. With command:
 # ifconfig eth0 mtu 1496
  • With the DomUs bridged to VLAN interfaces, some optimizations need to be disabled or tcp and udp connections will fail. This is done by disabling transmit checksum offloading:
 # ethtool -K eth0 tx off
  • Need further test in the production environment.

Xen Networking with bonding

              PRT0 PRT1                       PRT2 PRT3
                |   |                           |   |
 +--------------+---+---------------------------+---+--------------+
 |              |   |                           |   |              |
 |            eth0 eth1                       eth2 eth3            |
 |              |   |                           |   |              |
 |              +-+-+                           +-+-+              |
 |                |                               |                |
 | +--------------+--------------+ +--------------+--------------+ |
 | |              |              | |              |              | |
 | |            bond0            | |            bond1            | |
 | |                             | |                             | |
 | | xenbr0       vif1.0  vif1.1 | |  vif2.0  vif2.1      xenbr1 | |
 | |                |       \    | |    /       |                | |
 | +---^------------+---------\--+ +--/---------+------------^---+ |
 |     |            |           \   /           |            |     |
 |     |     +------+-------------X-------------+------+     |     |
 |     |     |      |           /   \           |      |     |     |
 |     |     | +----+---------/--+ +--\---------+----+ |     |     |
 |     |     | |    |       /    | |    \       |    | |     |     |
 |     |     | |  eth0    eth1   | |   eth0   eth1   | |     |     |
 |     |     | |    |       |    | |    |       |    | |     |     |
 |   +-+-+   | |  +-+-+   +-+-+  | |  +-+-+   +-+-+  | |   +-+-+   |
 |   |   |   | |  |   |   |   |  | |  |   |   |   |  | |   |   |   |
 |  www ssh  | | www ssh ftp pop | | www ssh ftp pop | |  ftp pop  |
 |           | |                 | |                 | |           |
 |  Domain0  | |     Domain1     | |     Domain2     | |  Domain0  |
 +-----------+ +-----------------+ +-----------------+ +-----------+

Notes:

  • Need some more destructive testing.

Xen Networking with vlan on bonding

              PRT0 PRT1                       PRT2 PRT3
                |   |                           |   |
 +--------------+---+---------------------------+---+--------------+
 |              |   |                           |   |              |
 |            eth0 eth1                       eth2 eth3            |
 |              |   |                           |   |              |
 |              +-+-+                           +-+-+              |
 |                |                               |                |
 |              bond0                           bond1              |
 |                |                               |                |
 | +--------------+--------------+ +--------------+--------------+ |
 | |              |              | |              |              | |
 | |          bond0.100          | |          bond1.200          | |
 | |                             | |                             | |
 | | xenbr0       vif1.0  vif1.1 | |  vif2.0  vif2.1      xenbr1 | |
 | |                |       \    | |   	/       |                | |
 | +---^------------+---------\--+ +--/---------+------------^---+ |
 |     |            |           \   /           |            |     |
 |     |     +------+-------------X-------------+------+     |     |
 |     |     |      |           /   \           |      |     |     |
 |     |     | +----+---------/--+ +--\---------+----+ |     |     |
 |     |     | |    |       /    | |    \       |    | |     |     |
 |     |     | |  eth0    eth1   | |   eth0   eth1   | |     |     |
 |     |     | |    |       |    | |    |       |    | |     |     |
 |   +-+-+   | |  +-+-+   +-+-+  | |  +-+-+   +-+-+  | |   +-+-+   |
 |   |   |   | |  |   |   |   |  | |  |   |   |   |  | |   |   |   |
 |  www ftp  | | www ftp ssh dns | | www ftp ssh dns | |  ssh dns  |
 |           | |                 | |                 | |           |
 |  Domain0  | |     Domain1     | |     Domain2     | |  Domain0  |
 +-----------+ +-----------------+ +-----------------+ +-----------+


Notes:

  • The connections at the top are switch ports - probably on 2 switches with an ISL
  • bond0 has eth0 and eth1 ; bond1 has eth2 and eth3
  • In the VMs eth0 maps to bond0.100 and eth1 maps to bond1.200
  • Protocols suggest a service VLAN (100) and a mgmt VLAN (200)

Collection of Examples

this is a collection of configurations that can help you to understand how it is working in detail and rapidly deploy one of them.

if you want to add a configuration to this list, please look at http://wiki.xensource.com/xenwiki/ under "Join Wiki as a Contributor"

Reference

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