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Excessive moh multicast traffic

renato.guimaraes
Beginner
Beginner

So I stumbled upon this while reading traffic on our Sonicwall router and noticed that we're dropping about 50 packets per seconds. Is there any way we can disable multicast moh 239.10.16.16 port 2000 on the telephony-service section without affecting moh?

This is on our UC540.

Thanks

-Renato

16 REPLIES 16

Alexander Maroukian
Rising star
Rising star

Hi Renato,

You can filter multicast on the switches or other devices but you need it for MoH and on ports where the phones are connected. You can use IGMP on the switch to control the multicast flow.

Best regards,

Alexander

Arturo Bianchi
Beginner
Beginner

Hi,

You can disable MoH to internal calls on CCA and the network will be quieter . MoH will continue to work with external calls; I do not think you can do much more, at least I seem to remember that the issue has been addressed in other threads.

NB: In the past I tried to see if it was possible to confine the multicast on VLAN Voice, but nobody has responded ...

73,

Arturo.

Sent from Cisco Technical Support iPhone App

Revised by Arturo Bianchi via web after lunch :-)

I will still need moh for external calls and internal, I just don't want my sonicwall router seeing those multicast packets.

We have Cisco Esw 520 at each office with 7942s connected at each port.

50 (or even 500, ro 5000) pps is not a problem even for a consumer-grade network device.

I understand, but I would prefer to limit these multicast packets to the voice vlan than to every port on the switch.

Isn't there a way to do this?

Yes.  no multicast moh 239.10.16.16 port 2000.  Enter that command under the telephony-service section. You will go from multicast to unicast and in some cases you may need to reboot the router for this to take effect. Multicast is a more efficient way to go about using MOH because the router doesn't need to create a separate RTP stream for each endpoint.  If you have many people being put on hold at once I would leave multicast enabled because it will preserve bandwidth. 

To keep it very simple, using multicast is like a radio.  The tower broadcast the signal over a certain frequency (IP address) and you can only hear the music (MOH) if you tune in.  If it were unicast, a separate connection would need to be created for everyone.

To keep it very simple, using multicast is like a radio.  The tower  broadcast the signal over a certain frequency (IP address) and you can  only hear the music (MOH) if you tune in.  If it were unicast, a  separate connection would need to be created for everyone.

5 Stars for this, love it

Cheers,

David.

Cheers, David Trad. **When you rate a persons post, you are indicating a thank you or that it helped, but at the same time you are also helping to maintain the community spirit - You don't have to rate posts and you wont be looked down upon :) *

Arturo Bianchi ha scritto:

I seem to remember that the issue has been addressed in other threads.

Hi,

here's one where I was there too: https://supportforums.cisco.com/message/3274084 (unanswered about the possibility of reducing traffic...). In fact, determined that it is an advantage to use the multicast (less CPU and traffic when used for more extentions), what I still wonder: it is possible to confine the multicast on voice vlan? And anyway, why not run 'on demand'.... If no one has to go on hold, it is useless to transmit all that multicast traffic, 24/24 hours and out of the phone network! It is not green...

73,

Arturo.

From a operating point of view. CME doesn't have a "voice VLAN". It will use all the LAN interfaces in the router to handle calls and will consider them "local" for the purpose of multicast. If you want to prevent it from sending multicast on some interface, you can use an ip access-group.

Then, I don't know why CME doesn't stop MoH when nobody his on hold, but I suspect there are good reasons. Also park slots do hear MoH, there can be more complications... Again, 50 pps is really nothing at all.

Paolo Bevilacqua ha scritto:

Again, 50 pps is really nothing at all.

Paolo, interesting notes on CME!  Did not see only agree on an issue: 50pps may be too many, when useless.   Increase only the entropy of the system. This may be an academic discussion and minor; however, at least I'm curious to read the authoritative considerations of Cisco staff!

73,

Arturo.

Thank you for the appreciation.

Regarding useless packets, try taking a look to "show ip error" or even better a packet capture, on any LAN that exists in the world.

I can assure you, you will find much worst bothering packets than CME MoH.

danielciscoswart
Beginner
Beginner

I had the same problem not long ago

Created an extended ACL to keep the multi casts from the DATA vlan.

So if I wanted to do this on my UC's, would this be correct?

# conf t

(config)# ip access-list 111 deny udp any host 239.10.16.16 eq 2000

(config)# interface vlan1

(config-if)# ip access-group 111 out

Thanks

-Renato

renato.guimaraes
Beginner
Beginner

I tried inputting those commands and it didn't work.

Any ideas?

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