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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 & 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      FastEthernet1/0/22       v2/S   1      30     1       Vlan12                   v2/S   0      30     1
WAN#sh ip pim interface

Address          Interface                Ver/   Nbr    Query  DR     DR
Mode   Count  Intvl  Prior       FastEthernet0/0.20       v2/S   0      30     1     FastEthernet0/0.22       v2/S   0      30     1      FastEthernet0/1          v2/S   1      30     1

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):, Static
RP: (?)

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 ( – in the “Address” field. I have used 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://” 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://” 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 ( If clients are joined for this group you would see (*,G) entry as well.

CAT2#sh ip mroute | in
(*,, 00:09:25/stopped, RP, flags: SJC
(,, 00:07:50/00:02:58, flags: T

WAN#sh ip mroute
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

(*,, 00:11:44/stopped, RP, flags: SPF
Incoming interface: FastEthernet0/1, RPF nbr
Outgoing interface list: Null

(,, 00:11:44/00:03:29, flags: FT
Incoming interface: FastEthernet0/0.22, RPF nbr
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