[libvirt-users] What's the best way to make use of VLAN interfaces with VMs?
Richard Achmatowicz
rachmato at redhat.com
Tue Dec 3 16:36:51 UTC 2019
Laine
I made the change and I can now ping across both bridges: br1
(192.168.0.0/24) and br1600 (192.168.1.0/24):
br1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.0.110 netmask 255.255.255.0 broadcast 192.168.0.255
inet6 fe80::1e98:ecff:fe1b:276d prefixlen 64 scopeid 0x20<link>
ether 1c:98:ec:1b:27:6d txqueuelen 1000 (Ethernet)
RX packets 21608 bytes 10289553 (9.8 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1372 bytes 131012 (127.9 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
br1600: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.1.110 netmask 255.255.255.0 broadcast 192.168.1.255
inet6 fe80::1e98:ecff:fe1b:276d prefixlen 64 scopeid 0x20<link>
ether 1c:98:ec:1b:27:6d txqueuelen 1000 (Ethernet)
RX packets 3429 bytes 173404 (169.3 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 112 bytes 9490 (9.2 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
// ping to another host with the same bridge br1 defined on 192.168.0.120
[root at clusterdev01 ~]# ping 192.168.0.120
PING 192.168.0.120 (192.168.0.120) 56(84) bytes of data.
64 bytes from 192.168.0.120: icmp_seq=1 ttl=64 time=0.481 ms
64 bytes from 192.168.0.120: icmp_seq=2 ttl=64 time=0.244 ms
64 bytes from 192.168.0.120: icmp_seq=3 ttl=64 time=0.242 ms
64 bytes from 192.168.0.120: icmp_seq=4 ttl=64 time=0.244 ms
64 bytes from 192.168.0.120: icmp_seq=5 ttl=64 time=0.237 ms
^C
// ping to another host with the same bridge br1600 defined on 192.168.1.120
[root at clusterdev01 ~]# ping 192.168.1.120
PING 192.168.1.120 (192.168.1.120) 56(84) bytes of data.
64 bytes from 192.168.1.120: icmp_seq=1 ttl=64 time=0.316 ms
64 bytes from 192.168.1.120: icmp_seq=2 ttl=64 time=0.245 ms
64 bytes from 192.168.1.120: icmp_seq=3 ttl=64 time=0.176 ms
64 bytes from 192.168.1.120: icmp_seq=4 ttl=64 time=0.213 ms
^C
However, for some reason, multicast has stopped working across the
bridge interface, when it was working in the previous configuration
(with br1 and br1.600).
I test multicast using a multicast test app, binding the receiver to br1
on one host (192.168.0.120) and then binding the sender on br1 on
another host (192.168.0.110). I also start an instance of tshark on each
host to check which packets are being sent across. The multicast packets
are seen by tshark to be crossing the bridge but for some reason the
receiver app does not receive them. The bridges also have the
multicast_querier and multicast_snooping flags enabled (e.g. for br1 on
both hosts):
[root at clusterdev01 ~]# cat /sys/class/net/br1/bridge/multicast_querier
1
[root at clusterdev01 ~]# cat /sys/class/net/br1/bridge/multicast_snooping
1
[root at clusterdev02 ~]# cat /sys/class/net/br1/bridge/multicast_querier
1
[root at clusterdev02 ~]# cat /sys/class/net/br1/bridge/multicast_snooping
1
// 1. start multicast test app sender and send packet across br1 (the
multicast address of 239.11.12.13 is fixed for both apps, as well as
multicast port 5555)
[root at clusterdev01 bridge-multicast-test]# ./start-ipv4-mcast-sender.sh
192.168.0.110
Socket #1=0.0.0.0/0.0.0.0:5555, ttl=32, bind interface=/192.168.0.110
> 1234567890
>
// 2. tshark on the sending host after sending packet
[root at clusterdev01 ~]# tshark -i br1 -f "igmp or host 239.11.12.13"
Running as user "root" and group "root". This could be dangerous.
Capturing on 'br1'
1 0.000000000 192.168.0.110 → 239.11.12.13 UDP 52 5555 → 5555 Len=10
2 55.389831698 0.0.0.0 → 224.0.0.1 IGMPv2 60 Membership
Query, general
3 60.194658894 192.168.0.115 → 224.0.0.251 IGMPv2 46 Membership
Report group 224.0.0.251
// 3. tshark on the receiving host across bridge br1
[root at clusterdev02 ~]# tshark -i br1 -f "igmp or host 239.11.12.13"
Running as user "root" and group "root". This could be dangerous.
Capturing on 'br1'
1 0.000000000 192.168.0.120 → 224.0.0.22 IGMPv3 54 Membership
Report / Join group 239.11.12.13 for any sources
2 0.902032534 192.168.0.120 → 224.0.0.22 IGMPv3 54 Membership
Report / Join group 239.11.12.13 for any sources
3 41.448921858 192.168.0.110 → 239.11.12.13 UDP 60 5555 → 5555 Len=10
// 4. previously started multicast test app receiver and no packet received
[root at clusterdev02 bridge-multicast-test]#
./start-ipv4-mcast-receiver.sh 192.168.0.120
Socket=0.0.0.0/0.0.0.0:5555, bind interface=/192.168.0.120
// NO PACKET APPEARS HERE :-(
It's puzzling that the packet is seen to arrive on clusterdev02 but is
not received by the test app. It's also odd to see IGMPv3 messages on
the receiver and IGMPv2 messages on the sender.
Investigating ....
Richard
On 11/29/19 12:15 PM, Richard Achmatowicz wrote:
> Hi Laine
>
> What you have suggested sounds eminently reasonable. Thanks for your
> advice. I'm going to give it a shot and report back.
>
> Richard
>
> On 11/27/19 1:38 PM, Laine Stump wrote:
>> On 11/26/19 11:07 PM, Richard Achmatowicz wrote:
>>> Hello
>>>
>>> I have a problem with attaching VMs to a VLAN interface.
>>>
>>> Here is my setup: I have several physical hosts connected by a
>>> physical switch. Each host has two NICs leading to the switch,
>>> which have been combined into a team, team0. Each host a has a
>>> bridge br1, which has team0 as a slave. So communication between
>>> hosts is based on the IP address of bridge br1 on each host.
>>>
>>> Up until recently, using libvirt and KVM, I was creating VMs which
>>> had one interface attached the default virtual network and one
>>> interface attached to the bridge:
>>>
>>> virt-install ... --network network=default --network bridge=br1 ...
>>>
>>> I would then statically assign an IP address to the bridge interface
>>> on the guest when installing the OS.
>>>
>>> A few days ago, a VLAN was introduced to split up the network. I
>>> created a new VLAN interface br1.600 on each of the hosts. My
>>> initial attempt was to do try this:
>>>
>>> virt-install ... --network network=default --network bridge=br1.600 ...
>>>
>>> which did not work. It then dawned on me that a VLAN interface and a
>>> bridge aren't treated the same. So I started to look for ways to
>>> allow my VMs to bind to this new interface.
>>>
>>> This would seem to be a common situation. What is the best way to
>>> work around this?
>>>
>>> Both the host bridge and the host VLAN interface already have their
>>> assigned IP addresses and appear like this in libvirt:
>>>
>>> [root at clusterdev01 ]# ifconfig
>>> br1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
>>> inet 192.168.0.110 netmask 255.255.255.0 broadcast
>>> 192.168.0.255
>>> inet6 fe80::1e98:ecff:fe1b:276d prefixlen 64 scopeid
>>> 0x20<link>
>>> ether 1c:98:ec:1b:27:6d txqueuelen 1000 (Ethernet)
>>> RX packets 833772 bytes 2976958254 (2.7 GiB)
>>> RX errors 0 dropped 0 overruns 0 frame 0
>>> TX packets 331237 bytes 23335124 (22.2 MiB)
>>> TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
>>>
>>> br1.600: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
>>> inet 192.168.1.110 netmask 255.255.255.0 broadcast
>>> 192.168.1.255
>>> inet6 fe80::1e98:ecff:fe1b:276d prefixlen 64 scopeid
>>> 0x20<link>
>>> ether 1c:98:ec:1b:27:6d txqueuelen 1000 (Ethernet)
>>> RX packets 189315 bytes 9465744 (9.0 MiB)
>>> RX errors 0 dropped 0 overruns 0 frame 0
>>> TX packets 302 bytes 30522 (29.8 KiB)
>>> TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
>>>
>>> [root at clusterdev01]# virsh iface-list --all
>>> Name State MAC Address
>>> ---------------------------------------------------
>>> br1 active 1c:98:ec:1b:27:6d
>>> br1.600 active 1c:98:ec:1b:27:6d
>>>
>>> [root at clusterdev01 sysadmin]# virsh iface-dumpxml br1.600
>>> <interface type='vlan' name='br1.600'>
>>> <protocol family='ipv4'>
>>> <ip address='192.168.1.110' prefix='24'/>
>>> </protocol>
>>> <protocol family='ipv6'>
>>> <ip address='fe80::1e98:ecff:fe1b:276d' prefix='64'/>
>>> </protocol>
>>> <link state='up'/>
>>> <vlan tag='600'>
>>> <interface name='br1'/>
>>> </vlan>
>>> </interface>
>>>
>>> I tried following some suggestions which wrapped the vlan interface
>>> in a bridge interface, but in ended up trashing the br1.600
>>> interface which was originally defined on the host.
>>>
>>> Is there a failsafe way to deal with such a situation? Am I doing
>>> something completely wrong here? In would like br1.600 to behave
>>> like br1 .....
>>>
>>> Any suggestions or advice greatly appreciated.
>>
>>
>> I guess what you need is for all the traffic from your guests to go
>> out on the physical network tagged with vlan id 600, and you want
>> that to be transparent to the guests, right?
>>
>> The simplest way to handle this is to create a vlan interface off of
>> the ethernet that you have attached to br1 (not br1 itself), so it
>> would be named something like "eth0.600", and then create a new
>> bridge (call it, say "br600") and attach eth0.600 to br600. Then your
>> guests would be created with "--network bridge=br600"
>>
>> (Note that Linux host bridges do now support vlan tagging (and maybe
>> even trunking) at the port level, but libvirt hasn't added support
>> for it. (in other words, "Patches Welcome!" :-))
>>
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