Multicast frames are not transmitting between KVM hosts.

Issues related to configuring your network
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delhi.pnr
Posts: 7
Joined: 2016/09/18 14:50:30

Multicast frames are not transmitting between KVM hosts.

Post by delhi.pnr » 2016/09/18 15:22:05

Hi Team,

I hope you are doing well.

I am very excited to write my first post on this forum.

Please help me on the below issue and kindly let me in the case of any additional information required.


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centos version and system outputs:

[root@localhost nikumar]# rpm --query centos-release
centos-release-6-8.el6.centos.12.3.x86_64
[root@localhost nikumar]#

[root@localhost nikumar]# virsh net-info private1
Name private1
UUID e405096d-18d1-366e-0f33-0729a0c7bdd8
Active: yes
Persistent: yes
Autostart: yes
Bridge: virbr1

[root@localhost nikumar]#

[root@localhost nikumar]# ifconfig virbr1
virbr1 Link encap:Ethernet HWaddr 52:54:00:2C:C7:11
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)

[root@localhost nikumar]# brctl show virbr1
bridge name bridge id STP enabled interfaces
virbr1 8000.5254002cc711 no virbr1-nic
vnet17
vnet3
[root@localhost nikumar]#

[root@localhost nikumar]# brctl showstp virbr1
virbr1
bridge id 8000.5254002cc711
designated root 8000.5254002cc711
root port 0 path cost 0
max age 19.99 bridge max age 19.99
hello time 1.99 bridge hello time 1.99
forward delay 0.00 bridge forward delay 0.00
ageing time 299.95
hello timer 0.16 tcn timer 0.00
topology change timer 0.00 gc timer 0.16
hash elasticity 4 hash max 512
mc last member count 2 mc init query count 2
mc router 1 mc snooping 0
mc last member timer 0.99 mc membership timer 259.96
mc querier timer 254.96 mc query interval 124.98
mc response interval 9.99 mc init query interval 31.24
flags


virbr1-nic (0)
port id 0000 state disabled
designated root 8000.5254002cc711 path cost 100
designated bridge 8000.5254002cc711 message age timer 0.00
designated port 8001 forward delay timer 0.00
designated cost 0 hold timer 0.00
mc router 1
flags

vnet17 (0)
port id 0000 state forwarding
designated root 8000.5254002cc711 path cost 100
designated bridge 8000.5254002cc711 message age timer 0.00
designated port 8003 forward delay timer 0.00
designated cost 0 hold timer 0.00
mc router 1
flags

vnet3 (0)
port id 0000 state forwarding
designated root 8000.5254002cc711 path cost 100
designated bridge 8000.5254002cc711 message age timer 0.00
designated port 8002 forward delay timer 0.00
designated cost 0 hold timer 0.00
mc router 1
flags

[root@localhost nikumar]#

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Topology:

<VM1> interface em0 <virbr0> interface em0 <VM2>

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Issue:
virbr0 is not passing the multicast frames to each other VM's.

How do I verify that both routers are sending the multicast frames on virbr0?
I had a Wireshark capture and the multicast frame was captured from both of the VM's.

Unicast ethernet frames and multicast ethernet frames(ff:ff:ff:ff:ff:ff): are working fine.

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Steps to reproduced:

Connect two VM's to KVM bridge and send LACP/LLDP traffic on the interfaces. If neighborship is not up then you have reproduced the issue.


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What troubleshooting has been done:

I have disabled the multicast_snooping.

[root@localhost net]# echo 0 >/sys/devices/virtual/net/virbr1/bridge/multicast_snooping
[root@localhost net]# cat /sys/devices/virtual/net/virbr1/bridge/multicast_snooping
0
[root@localhost net]#

Did I reboot any daemon after making the changes?

Yes, I have rebooted my whole system.

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What is the exact requirement:

If any VM sending the multicast frame to virbr0 the frame should reach to all VM's interfaces connected to virbr0.

For example the LLDP traffic:

01-80-C2-00-00-00, or 01-80-C2-00-00-03, or 01-80-C2-00-00-0E
Type Field : 0x88CC Link Layer Discovery Protocol

So do I need virbr0 as the Layer1 hub?

Yes, this is correct.
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How I have found this issue:

I was implementing the 802.3ad link aggregation between two VM's and I found that the LACP frames were not received on both interfaces.

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Regards:

Nishant

delhi.pnr
Posts: 7
Joined: 2016/09/18 14:50:30

Re: Multicast frames are not transmitting between KVM hosts.

Post by delhi.pnr » 2016/09/18 17:39:40

i have tried the below workaround without success.

[root@localhost nikumar]# brctl setageing virbr1 0
[root@localhost nikumar]# brctl setfd virbr1 0
[root@localhost nikumar]# brctl showstp virbr1


delhi.pnr
Posts: 7
Joined: 2016/09/18 14:50:30

Re: Multicast frames are not transmitting between KVM hosts.

Post by delhi.pnr » 2016/09/20 19:30:02

I have asked my requirement in a very simple way. Please find the below link

viewtopic.php?f=16&t=59390

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