To refresh my knowledge on multicast I have created this basic test set up in my home lab. During lab exam we do not have real multicast application to test & rely on “ip igmp join-group x.x.x.x” command to test the service.
But in real world multicast applications/networks you will not see this command configured. Below example shows how to use a real world application to check multicast service on your network.
For this lab, I have used VLC media player as the multicast application. In Laptop-1, I am streaming a video to a multicast address( in my case 239.1.1.1) & Laptop-2 will act as multicast receiver. I have used 3750 (layer 3) & 2960 (layer 2) switches & 1841 router to simulate a WAN connection.
To enable multicast on layer 3 network devices(3750 & 1841 in my case) you have to configure “ip multicast-routing” on the global CLI. In switch platform additional “distribuited” keyword required at the end (i.e. ip multicast-routing distributed)
Next step is to enable PIM (Protocol Independent Multicast) at the interface level(always L3 physical interfaces or SVI interfaces). Multicast always rely on the underlying IGP routing & that should work properly prior to configuring multicast. There are primarily two mode of PIM configuration (sparse mode & dense mode) available. I have chosen to use “sparse mode” in this lab.
“ip pim sparse-mode” is the command to be configured to enable PIM on the interface level. “show ip pim interface”could be used to verify that you have configured PIM on required interfaces.
CAT2#sh ip pim interface
Address Interface Ver/ Nbr Query DR DR
Mode Count Intvl Prior
172.16.99.2 FastEthernet1/0/22 v2/S 1 30 1 172.16.99.2
10.10.12.1 Vlan12 v2/S 0 30 1 10.10.12.1
WAN#sh ip pim interface
Address Interface Ver/ Nbr Query DR DR
Mode Count Intvl Prior
10.10.20.1 FastEthernet0/0.20 v2/S 0 30 1 10.10.20.1
10.10.22.129 FastEthernet0/0.22 v2/S 0 30 1 10.10.22.129
172.16.99.1 FastEthernet0/1 v2/S 1 30 1 172.16.99.2
In PIM sparse mode we have to configure RP (Rendezvous Point). Though there are multiple ways of configuring this I used static configuration for the simplicity. “ip pim rp-address x.x.x.x” command can be used to configure it on all multicast enabled (pim configured devices) devices including RP itself(In my case CAT2 ). “show ip pim rp mapping” command can be used to verify it.
CAT2#sh ip pim rp mapping
PIM Group-to-RP Mappings
Group(s): 224.0.0.0/4, Static
RP: 10.10.10.3 (?)
That’s all & you are ready to use the network for multicast services. In my Laptop-1 I have a local video that I would use to stream as multicast source.
Open VLC media player (it is freely available & you can download it from here http://www.videolan.org/vlc/index.html)
Click “Media” tab & select “Stream”
Select your video file by clicking “Add” button & then click “Stream” button in the bottom.
Click “Next” to configure the multicast address you want to use.
By clicking the drop down menu to select “RTP/MPEG Transport System” & then click “Add “ button next to the drop down menu. If you want to watch the video locally while streaming click “Display locally” checkbox.
When the “Add” button clicked, you will get the below screen & enter a multicast address (224.0.0.1 – 239.255.255.255) in the “Address” field. I have used 239.1.1.1 as multicast address. If you want to change the udp port number used change the “Base Port” value.
Leave the default Transcoding “Video – H.264 + MP3(MP4) for the good quality & check the “Activate Transcoding” to activate it. If your video is high quality & you do not want to use this codec leave this check box “unchecked”
Click “Next “ to add configure “SAP announce” & TTL for your multicast stream. In my example receiver will be on different network & few hops away (so TTL value should be greater than 1). Instead of using “rtp://239.1.1.1:5004” at the multicast receiver & automatically announce stream use a name for “SAP announce” field. Once everything done click “Stream” button.
Now go to “Laptop-2 “ & open the VLC player. Click “Media” & then “Open Network Stream”
Then type “rtp://239.1.1.1:5004” in “Please enter a network URL section”. Your can watch your video from the Laptop 2. If you used a different udp port use that number instead of default 5004.
Now here you are…..your multicast streaming is working. ( Here is my video used for this lab. Since I copy it from youtube, I have linked the original video to this post. It’s a song I love to listen )
Now if you go to CAT2 & WAN & type “show ip mroute” command you would be able to verify the multicast traffic is working . If everything is fine, you would see (S,G) entry which show the multicast source (Laptop-1 in my case) & the group address (239.1.1.1). If clients are joined for this group you would see (*,G) entry as well.
CAT2#sh ip mroute | in 239.1.1.1
(*, 239.1.1.1), 00:09:25/stopped, RP 10.10.10.3, flags: SJC
(10.10.22.131, 239.1.1.1), 00:07:50/00:02:58, flags: T
WAN#sh ip mroute 239.1.1.1
IP Multicast Routing Table
Flags: D – Dense, S – Sparse, B – Bidir Group, s – SSM Group, C – Connected,
L – Local, P – Pruned, R – RP-bit set, F – Register flag,
T – SPT-bit set, J – Join SPT, M – MSDP created entry,
X – Proxy Join Timer Running, A – Candidate for MSDP Advertisement,
U – URD, I – Received Source Specific Host Report,
Z – Multicast Tunnel, z – MDT-data group sender,
Y – Joined MDT-data group, y – Sending to MDT-data group
Outgoing interface flags: H – Hardware switched, A – Assert winner
Timers: Uptime/Expires
Interface state: Interface, Next-Hop or VCD, State/Mode
(*, 239.1.1.1), 00:11:44/stopped, RP 10.10.10.3, flags: SPF
Incoming interface: FastEthernet0/1, RPF nbr 172.16.99.2
Outgoing interface list: Null
(10.10.22.131, 239.1.1.1), 00:11:44/00:03:29, flags: FT
Incoming interface: FastEthernet0/0.22, RPF nbr 0.0.0.0
Outgoing interface list:
FastEthernet0/1, Forward/Sparse, 00:04:33/00:02:40
Related Posts
1. Configuring Multicast on WLC
2. Wireless Multicast is not working – Why ?
3. Understanding “VideoStream” feature
4. IGMP Basics
5. Multicast Address Allocation
mrn-cciew 
Hi. I’m also taking CCIEW in 1302.13. Could you please help me understand MSDP peering with shared rp-address w/ACL and if all controllers should use same multicast group.
Hi JT,
I’ll see what can I do for this(hopefully should be able to do a post on this topic). My weak areas are Autonomous & Security stuff. So planning to allocate most of time on those next 3-4 weeks. By the way when do you plan for your 1st attempt ?
HI JT,
I have publish a post on Anycast MSDP configuration. Hope that helps for your queries.
Rasika
Hi nayarsi, very good tutorial.I am newbie in multicasting igmp. Is this 239.1.1.1 ip is of the switch ? Or this is only virtual ip ?
Hi Stole,
In multicast these group addresses are not configured anywhere in the switches.
When you configure a multicast source (streaming servers) with particular group address (239.1.1.1 in this case) that traffic goes to a switch where streaming server connect to.
Unless no receivers/clients requesting that traffic (via IGMP join to this group address) that traffic will not flow further. When clients join this group address multicast traffic will be flow to that switch.
It is one to many type of communication & conserve bandwidth as single copy goes to multiple client (opose to 1:1 in unicast which is not efficient in this scenario)
HTH
Rasika
Hi Nayarasi, Very good article. I have many doubts in understanding the multicast network setup involving all the components IGMP, PIM and multicast routing. lease can you share your email id for me to share my doubts in detail ?
Thank you Vinayak, I have shared my details with you on LinkedIn
Rasika
I am trying to set this up using a DD-WRT router to a DSL ISP and a Huawei B681 Wireless Gateway. Do you think these devices will work or should I get something else.
I haven’t use/configure these devices. So difficult to advise about it
HTH
Rasika
Hello, when I emitted teh route doesnt add to de mroute table adn I dont see any igmp packets. When add a receiver I see the mroute with (*,Group ADD) and see the iGMP packets. Im a bit confused about how the router add the (S,G) route to its table, It depends on IGMP also?
Thanks.
Dear Rasika,
First off, thank you so much for your valuable forums on Wireless technologies. They are extremely helpful.
I’m trying to test multicast in my lab setup. The setup is very simple, please refer below.
Multicast Sender ——- NW Switch(3560)———-WLC 2504
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3802 AP —– SSID ——– Multicast receiver
I configured Multicast on WLC already. Just want to understand what all config will be required on the Switch to allow multicast. We did configure IGMP snooping and PIM on the switch.
Thanks
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