[Xen-users] Multicast problems when VM are located on different Xen servers

[Jason Friedrich <jfriedrich@xxxxxxxxx>]

XenServer build date: 2010-11-30
XenServer build number: 39265p
XenServer version: 5.6 Feature Pack 1
Guest OS: CentOS 5.6
Guest Kernel: 2.6.18-238.9.1.el5xen

Hi everyone, 

we have set up several Xen servers with the version mentioned above. The 
version is the same on all servers, the kernel is the default one, not patches 
or self compiled versions. Each Xen server has 6 network interfaces (eth0 to 
eth5), eth0 is always the management interface. The Xen servers are connected 
to each other through a switch, there is no router in-between.

eth0 Link encap:Ethernet HWaddr 78:2B:CB:15:C3:EB
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:38509 errors:0 dropped:0 overruns:0 frame:0
TX packets:39420 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:4805538 (4.5 MiB) TX bytes:21756593 (20.7 MiB)
Interrupt:36 Memory:d8000000-d8012800

eth1 Link encap:Ethernet HWaddr 78:2B:CB:15:C3:EC
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:6825 errors:0 dropped:0 overruns:0 frame:0
TX packets:899 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:517621 (505.4 KiB) TX bytes:72630 (70.9 KiB)
Interrupt:48 Memory:da000000-da012800

eth2 Link encap:Ethernet HWaddr 00:1B:21:97:EE:C8
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:5802 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:421127 (411.2 KiB) TX bytes:0 (0.0 b)

eth3 Link encap:Ethernet HWaddr 00:1B:21:97:EE:C9
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:3992 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:285524 (278.8 KiB) TX bytes:0 (0.0 b)

eth4 Link encap:Ethernet HWaddr 00:1B:21:97:EE:CC
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:3763 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:274514 (268.0 KiB) TX bytes:0 (0.0 b)

eth5 Link encap:Ethernet HWaddr 00:1B:21:97:EE:CD
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:62839 errors:0 dropped:0 overruns:0 frame:0
TX packets:62839 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:41257281 (39.3 MiB) TX bytes:41257281 (39.3 MiB)

vif1.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF
UP BROADCAST RUNNING NOARP MULTICAST MTU:1500 Metric:1
RX packets:896 errors:0 dropped:0 overruns:0 frame:0
TX packets:6185 errors:0 dropped:6 overruns:0 carrier:0
collisions:0 txqueuelen:32
RX bytes:49416 (48.2 KiB) TX bytes:373088 (364.3 KiB)

xenbr0 Link encap:Ethernet HWaddr 78:2B:CB:15:C3:EB
inet addr:xxx.xxx.86.xxx Bcast:10.17.86.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:38250 errors:0 dropped:0 overruns:0 frame:0
TX packets:31612 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:4058735 (3.8 MiB) TX bytes:21159329 (20.1 MiB)

xenbr1 Link encap:Ethernet HWaddr 78:2B:CB:15:C3:EC
inet addr:xxx.xxx.22.xxx Bcast:10.17.23.255 Mask:255.255.254.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2931 errors:0 dropped:0 overruns:0 frame:0
TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:148857 (145.3 KiB) TX bytes:252 (252.0 b)

xenbr2 Link encap:Ethernet HWaddr 00:1B:21:97:EE:C8
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:5385 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:262617 (256.4 KiB) TX bytes:0 (0.0 b)

xenbr3 Link encap:Ethernet HWaddr 00:1B:21:97:EE:C9
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:3737 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:171902 (167.8 KiB) TX bytes:0 (0.0 b)

xenbr4 Link encap:Ethernet HWaddr 00:1B:21:97:EE:CC
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:3512 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:161552 (157.7 KiB) TX bytes:0 (0.0 b)

xenbr5 Link encap:Ethernet HWaddr 00:1B:21:97:EE:CD
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)

Now to the actual problem: 

When you have two CentOS VM, each with one network interface (located in the 
xxx.xxx.22.xxx network) running on the same Xen server, multicasting works 
perfectly.

When you migrate one of the VM to another Xen server, the multicasting is not 
working anymore! On the sender side, you see multicast traffic on the according 
vif and xenbr interface. But after that, no mc traffic can be seen via tcpdump.

Is there a way to tell Xen to forward multicast packages through the bridge to 
another Xen server?

Or is here perhaps multicast routing required, with a special kernel and a 
multicast routing daemon?

Has someone on this list experienced similar problems or, even better, has a 
working multicasting setup?

Regards,
 - Jason



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