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VEs and HNs in same subnets

2,743 bytes added, 13:20, 26 November 2013
Added GATEWAY to ifcfg-eth0 example.
This describes a method of setting up networking for a host and its VEs such that the networking configuration for the VEs can be configured exactly as if the VEs were standalone hosts of their own in the same subnets or VLAN as the host. This method makes use of the Virtual Ethernet device and bridges between the host and its containers. This technique has the advantage of allowing IPv6 network configurations to work on both VEs and hosts as they normally would. In particular, both hosts and VEs can use IPv6 autoconfiguration. The network configuration of a VE can be identical to that of a non-VE system.
In the following example the host has two physical interfaces and we are setting up the network configuration for VE 100. The host IP configuration is moved out of the ethN interface configs and into the vzbrN brN interface config scripts (ifcfg-vzbr0 br0 and ifcfg-vzbr1br1). Ie. the host IP configuration will now reside on the vzbrN brN interfaces instead of the ethN interfaces. The example also assumes IPv4 is configured statically, whereas IPv6 is auto-configured.
==Configure host bridge interfaces==
 
Steps 1 through 4 are done only once on the host.
 
1. (Optional) Verify that you can create a bridge interfaces for each physical interface on the host.
/usr/sbin/brctl addbr vzbr0br0 /usr/sbin/brctl addbr vzbr1br1
If the above commands do not work you may need to install the bridge-utils package.
2. Make note of the existing IP configuration in the hosts ifcfg-ethN files. Also, record the hardware MAC addresses of the ethernet interfaces from the output of 'ifconfig'.  /sbin/ifconfig eth0 /sbin/ifconfig eth1  Then, modify the ifcfg-ethN files on the host so that they ONLY bridge to the corresponding vzbrN brN interface. /etc/sysconfig/network-scripts/ifcfg-eth0 should look like:
DEVICE=eth0
BOOTPROTO=none
ONBOOT=yes
BRIDGE=vzbr0br0
Similarly ifcfg-eth1 will look like:
BOOTPROTO=none
ONBOOT=yes
BRIDGE=vzbr1br1
Note that the ifcfg-ethN files on the host do not contain any IP information anymore.
3. Create ifcfg-vzbrN brN files and copy the IP configuration that was previously in the ifcfg-ethN files into ifcfg-vzbrNbrN. Here's what host:/etc/sysconfig/network-scripts/ifcfg-vzbr0 br0 would look like assuming the IPv4 address is assigned statically and IPv6 auto-configuration (SLAAC) is used:
DEVICE=vzbr0br0
BOOTPROTO=static
IPADDR=xxx.xxx.xxx.xxx
NETMASK=aaa.aaa.aaa.aaa
ONBOOT=yes
TYPE=bridgeBridge MACADDR=mm:mm:mm:mm:mm:mm
Similarly, ifcfg-vzbr1 br1 should look like:
DEVICE=vzbr1br1
BOOTPROTO=static
IPADDR=yyy.yyy.yyy.yyy
NETMASK=bbb.bbb.bbb.bbb
ONBOOT=yes
TYPE=Bridge MACADDR=nn:nn:nn:nn:nn:nn Note that TYPE 'Bridge' is case-sensitive. Otherwise, the bridgeinterfaces will not initialize correctly during boot. The bridge MACADDR should be hard-coded to match the corresponding hardware MAC address of the ethernet interface. Otherwise the default behaviour is to use the lowest MAC address of all the interfaces in the bridge. This is to prevent the bridge MAC and any auto-configured IPv6 address on the bridge interface from changing as VEs are created, started, or stopped. 4. On the host, do a 'service network restart' and verify the host has both IPv4 and IPv6 connectivity to its brN interfaces.
4==Create the VE veth interfaces==5. On Create the hostVE as you normally would, except do a 'service network restart' and verify NOT specify any IP address, just the host has both IPv4 and IPv6 connectivity to its vzbrN interfaceshostname. Specifying an IP address during VE creation creates an unwanted venet interface which is not used in this configuration.
==Configure the VE veth interfaces==5. Create the VE as you normally would except do NOT specify any IP address, just the /usr/sbin/vzctl create 100 --ostemplate name --hostname. Specifying an IP address during VE creation creates an unwanted venet interface which is not used in this configuration.name
However, if the VE already exists, use vzctl to remove any venet devices - they will not be used:
/usr/sbin/vzctl set 100 --ipdel all --save
6. For each VE, create ethN devices (ignore warnings about "Container does not have configured veth") on the host:
/usr/sbin/vzctl set 100 --netif_add eth0--save /usr/sbin/vzctl set 100 --netif_add eth1--save
The above creates corresponding veth100.0 and veth100.1 devices on the host and updates the host /etc/vz/conf/100.conf file with generated MAC addresses for the veth devices. When the VE is started, the veth100.0 and veth100.1 devices will be automatically created on the host.
==Bridge the host and VE==
7. Next we add the host vethN interfaces to the host bridged interfaces (vzbrNbrN).
Create host:/etc/sysconfig/network-scripts/ifcfg-veth100.0
DEVICE=veth100.0
ONBOOT=yesno BRIDGE=vzbr0br0
Create host:/etc/sysconfig/network-scripts/ifcfg-veth100.1
DEVICE=veth100.1
ONBOOT=yesno BRIDGE=vzbr1br1 To make the above take effect, either start the VE,  /usr/sbin/vzctl start 100
To make the above take effect, either do another Or if it'service network restart' on the host, or s already started then manually add each VE interface to its corresponding bridge by runningusing:
/usr/sbin/brctl addif vzbr0 br0 veth100.0 /usr/sbin/brctl addif vzbr1 br1 veth100.1
8. Verify each bridge includes the host interface and the veth interfaces for each VE:
==Configure the VE networking==
9. In Enter the container create VE from the ifcfg network scripts for each interface eth0 and eth1. The scripts should look like standard ifcfg network scripts for a host.:
/usr/sbin/vzctl enter 100
After entering In the container create the ifcfg network scripts for each interface eth0 and eth1. The ifcfg-ethN files should look like standard ifcfg network scripts for a non-VE:host.
vi /etc/sysconfig/network-scripts/ifcfg-eth0
vi /etc/sysconfig/network-scripts/ifcfg-eth1
As noted above, the ifcfg-ethN files in the VE should be created to be identical to standard ifcfg-eth* files from a non-virtualized host. A minimum ifcfg-eth0 file using a static IPv4 address would have the following entries:  DEVICE=eth0 BOOTPROTO=static IPADDR=xxx.xxx.xxx.xxx NETMASK=yyy.yyy.yyy.yyy ONBOOT=yes GATEWAY=zzz.zzz.zzz.zzz
10. Initialize the interfaces and restart the network service on the container.
Alternatively, just restart the VE from the host.
==Enable bridging through the host firewall==11. Add FORWARD ACCEPT statements to Verify the host iptables and ip6tables for VE have connectivity to each VE IPv4 and IPv6 address. You do NOT need other as well as to enable any special the rest of the network forwarding via sysctl.
iptables:==Additional VEs== -A FORWARD -s xxx12.xxx For each additional VE, start at step #5.xxx.xxx -j ACCEPT -A FORWARD -d xxx.xxx.xxx.xxx -j ACCEPT
ip6tables:==Notes on IPv6 autoconfiguration== -A FORWARD -If your CT0 is also performing routing duties, you might chance upon the problem that IPv6 stateless autoconfiguration using radvd is not working for the CT's xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx -j ACCEPT -A FORWARD -d xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx -j ACCEPT. The description below is specific for a Debian (Lenny) CT0 and Debian (Squeeze) CT.
Then restart both iptables First check if your CT is actually receiving any router advertisements (RA's). This can be done by installing radvd (apt-get install radvd) and ip6tables running radvdump. Simply wait for the next round of RA's from radvd, or trigger it (by restarting radvd on CT0, for example). If you do not receive any RA's there is a more fundamental problem. The following only concerns the scenario where the CT receives RA's but does not configure the network interfaces accordingly. Do not forget to remove the host:radvd package after checking.
service iptables restartBecause CT0 is performing routing services, all or some values under /proc/sys/net/ipv6/conf/*/forwarding and under /proc/sys/net/ipv6/conf/*/mc_forwarding are set to 1. This appears to override the defaults for these values in the /proc filesystems for the CT's. Unless you explicitly disable forwarding in /etc/sysctl.conf, your CT will also use these values. This means that, to the IPv6 Neighbour Discovery Protocol (NDP) responsible for router advertisements and autoconfiguration, your CT is a router and therefore not allowed to use the RA's to configure the interfaces. To fix this, add or change the following lines to /etc/sysctl.conf '''''on the CT, not on CT0''''': service ip6tables restart<pre>net.ipv6.conf.all.forwarding=0net.ipv6.conf.all.mc_forwarding=0</pre>
The VE iptables and ip6tables configuration can be treated as fully independent of You may also want to explicitly disable IPv4 forwarding since the host iptables and ip6tables configurationCT is not a router.To do this, also change the line:<pre>net.ipv4.ip_forward=0</pre>
12. Verify Now reload sysctl on the host CT by executing<pre>sysctl -p</pre>and VE have connectivity to each other as well as you will be good to go. The CT will now autoconfigure the rest of network interfaces the networknext time it sees an RA.
13NOTE: Due to bug [http://bugzilla. For each additional VEopenvz.org/show_bug.cgi?id=1723 1723] this setup might not work: Enabling the routing on CT0 can effectively kill all IPv6 connectivity for the CT, depending on the setup. (This bug is reported to be solved since 2011-06-07, start at step #5so this shouldn't be an issue anymore.)
==See also==
* [[IPv6]]
* [[Virtual Ethernet device]]
* [[Differences between venet and veth]]
Tony
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