Multicast questions

[IT Services]

Good Morning.

We were looking to deploy wireless VoIP phones into our environment. These phones have a PTT feature which utilizes Multicast.

I was looking into configuring Multicast mode on the wireless controller and access points in our network. Do you think this is necessary or at least recommended for the PTT application or do I just let the unicast mode continue to function.

Also if we do enable multi-cast mode and videostream it is not supported on the Flex AP's. Would the Flex AP's still join the controllers or would we have to move the Flex AP's to another controller?

[Rasika Nayanajith]

Enabling or Disabling multicast does not have any impact to AP registration. So your Flex AP still can join your controller.

In general Multicast mode have advantages over Unicast mode from wireless controller's performance perspective (instead of sending same msg to every AP as unicast, it can send a single copy to a multicast address). In your case I am not too sure about whether multicast is a MUST or RECOMMENDED to have.

If you are deploying this voice services over flex AP & flex AP does not support multicast, then you may face issues if appication required multicast. which controller models do you have for this ?

HTH

Rasika

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[IT Services]

Wow. Sorry for not getting back to this sooner.

We have 3602i running in Flex Mode with Local Switch\Central Auth. The controller is 5508 running 7.4.110.0

Does the Flex AP's default to Multicast-Unicast even if Multicast-Multicast is set on the global controller config?

[Saravanan Lakshmanan]

multicast traffic forwarded from wireless to wired when flex local switching is used. nothing needs to be enabled on ap.

[IT Services]

Saravanan Lakshmanan wrote:
multicast traffic forwarded from wireless to wired when flex local switching is used. nothing needs to be enabled on ap.

I'm not sure we are on the same page.

I was just wondering if there was any issue with enabling Multicast mode (Multicast-to-Multicast) on the Controller that is servicing Flex Connect access points. Will the Flex Connect AP's still function and will they function as Multicast-to-Unicast mode?

[Rasika Nayanajith]

Yes, there won't be any issues of enabling Multicast-to-Multicast mode on your WLC while it servicing FlexConnect AP.

Video Stream (AP will unicast multicast frames) will only applicable to central switching WLAN of your flexconnect AP, all other scenario (local switching) it is not supported feature with flexconnect mode.

See below FlexConnect feature matrix for detail

http://www.cisco.com/en/US/products/ps10315/products_tech_note09186a0080b3690b.shtml

HTH

Rasika

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[Saravanan Lakshmanan · Accepted solution]

Does the Flex AP's default to Multicast-Unicast even if Multicast-Multicast is set on the global controller config?

//No, it doesn't receive Multicast packets from WLC.

Let see what're the parameters that can affect Multicast forwarding:

#WLC platform.

#Global AP Multicast mode config at WLC.

#Mode of the AP - Local, Flexconnect central switching.

#With flex Local switching, it doesn't even send/receive the packet to/from WLC, so it doesn't matter what Multicast mode is configured on wlc.

Multicast support on different WLC platforms:

#WLC 5500/WiSM2/8500 supports both Multicast and Unicast mode.

#WLC 2500 supports Multicast to Multicast only.

#WLC 7500 & vWLC supports Multicast to Unicast only. Supports Flex APs only.

#Flexconnect mode AP can't join Multicast group address configured at WLC -> AP mode Multicast to Multicast. Since it is not joined to the Multicast group, it can't receive Multicast packet that are sent by WLC(and Multicast packet sent by flex central switching will be received by local mode APs only). If Multicast needs to be forwarded for flexconnect central switching then configure AP mode Multicast to Unicast. Remember, it is global config that's applicable for local mode AP also.

#WLC 5500/WiSM2/8500 supports both Multicast and Unicast mode.

//When mix of local mode AP and flex central switching is used where flex centrally switched wlan need to forward/receive Multicast traffic then need to set "AP Multicast mode to Unicast only". (With Multicast mode enabled, WLC can't send one copy to the Multicast address and individual copies to the Flex mode APs.)

#WLC 2500 supports Multicast to Multicast only.

//Flex central switched APs can't receive Multicast packets since it doesn't support Unicast mode. Use Flex local switching as workaround in this case.

#WLC 7500 & vWLC supports Multicast to Unicast only. Supports Flex APs only.

//It supports only Flex APs, so Multicast to Unicast is the only applicable config that is allowed.

Since it is not cco documented, will try to address this on Multicast section of config guide.

[Rasika Nayanajith]

Hi Saravanan,

Thanks for covering everything related to WLC multicast in this response.

VIP endorsed

Regards

Rasika

[Saravanan Lakshmanan]

Hi Rasika

Glad to help

Thanks

Saravanan

[IT Services]

Any particular Multicast address range we should use? Just anyone not used in our network and not assigned to SSM or anything?

[Scott Fella]

Some of us here use 239.

Sent from Cisco Technical Support iPhone App

[IT Services]

Saravanan Lakshmanan wrote:
Does the Flex AP's default to Multicast-Unicast even if Multicast-Multicast is set on the global controller config?
//No, it doesn't receive Multicast packets from WLC.
Let see what're the parameters that can affect Multicast forwarding:
#WLC platform.
#Global AP Multicast mode config at WLC.
#Mode of the AP - Local, Flexconnect central switching.
#With flex Local switching, it doesn't even send/receive the packet to/from WLC, so it doesn't matter what Multicast mode is configured on wlc.
Multicast support on different WLC platforms:
#WLC 5500/WiSM2/8500 supports both Multicast and Unicast mode.
#WLC 2500 supports Multicast to Multicast only.
#WLC 7500 & vWLC supports Multicast to Unicast only. Supports Flex APs only.
#Flexconnect mode AP can't join Multicast group address configured at WLC -> AP mode Multicast to Multicast. Since it is not joined to the Multicast group, it can't receive Multicast packet that are sent by WLC(and Multicast packet sent by flex central switching will be received by local mode APs only). If Multicast needs to be forwarded for flexconnect central switching then configure AP mode Multicast to Unicast. Remember, it is global config that's applicable for local mode AP also.
#WLC 5500/WiSM2/8500 supports both Multicast and Unicast mode.
//When mix of local mode AP and flex central switching is used where flex centrally switched wlan need to forward/receive Multicast traffic then need to set "AP Multicast mode to Unicast only". (With Multicast mode enabled, WLC can't send one copy to the Multicast address and individual copies to the Flex mode APs.)
#WLC 2500 supports Multicast to Multicast only.
//Flex central switched APs can't receive Multicast packets since it doesn't support Unicast mode. Use Flex local switching as workaround in this case.
#WLC 7500 & vWLC supports Multicast to Unicast only. Supports Flex APs only.
//It supports only Flex APs, so Multicast to Unicast is the only applicable config that is allowed.
Since it is not cco documented, will try to address this on Multicast section of config guide.

So I read this again. Say we have Flex Central switching then we MUST configure AP unicast if the clients on the Flex AP need to be able to stream multicast? So if that is the case then the client just wont be able to join the multicast group?

[Saravanan Lakshmanan]

when AP mode being Multicast, hreap/flexconnect mode AP does not join multicast group, irrespective of their wlan being central/locally switched. possibly, it can carry central and locally switched wlan with same ssid/vlan, in this case all downstream multicast traffic will unnecessarily flood to flex APs at all sites due to all APs being joined to one Mcast group address(only AP local mode supported) if supported, also today ap is not smart enough(feature NA). future wlc mcast feature may have this enhancement.

#need to test if flex APs(when only locally switched wlan is used on it) can receive mcast packets when sent by wlan on local mode AP/flex AP with central switching, using AP mode unicast.

client joining Multicast group is different from AP joining Multicast group(when AP mode is Multicast) that i am trying to explain.

[IT Services]

Saravanan Lakshmanan wrote:
when AP mode being Multicast, hreap/flexconnect mode AP does not join multicast group, irrespective of their wlan being central/locally switched. possibly, it can carry central and locally switched wlan with same ssid/vlan, in this case all downstream multicast traffic will unnecessarily flood to flex APs at all sites due to all APs being joined to one Mcast group address(only AP local mode supported) if supported, also today ap is not smart enough(feature NA). future wlc mcast feature may have this enhancement.
#need to test if flex APs(when only locally switched wlan is used on it) can receive mcast packets when sent by wlan on local mode AP/flex AP with central switching, using AP mode unicast.
client joining Multicast group is different from AP joining Multicast group(when AP mode is Multicast) that i am trying to explain.

Pardon my ignorance. I am having a hard time following.

So i am looking to acheive more optimal Multicast networking for some wireless clients that will utilize multicast. For example:

* We have some spectralink wireless VoIP handsets. These handsets utilize PTT which is multicast. Should we change our AP multicast mode to multicast?

But that seems like it will cause adverse effects for Flex Connect AP's for sure.

So confused

[Saravanan Lakshmanan]

it is not your fault, CCO doc is unclear.

* We have some spectralink wireless VoIP handsets. These handsets utilize PTT which is multicast. Should we change our AP multicast mode to multicast?

//Yes, but the flex APs can't receive any Multicast because it require AP mode to be Unicast.

But that seems like it will cause adverse effects for Flex Connect AP's for sure.

//that's correct.

For optimization, you can still have AP mode Unicast and igmp snooping enabled, then it should send it only the APs, where clients are hanging off, who sent igmp join requests, for that mcast traffic.