Basic Multicast Lab

Posted on Posted in Multicast / Media stream, VideoStream

R6 has igmp join on it’s loopback 0. Verify that the RP/R2 has the entry in the mroute table. R4 should also have the 239.255.255.6 (star,g) entry for (*,239.255.255.6)


Note the other routers do not have the (*,g) entry. Example of R3’s show ip mroute

All of the routers should know who the RP is via static or auto-rp/BSR


igmp join group added to R6’s loopback 0


Packet capture taken at R2’s e0/1 interface


The reverse logic should be true. If R6 removes the igmp join command from its loopback0 interface we should see a join/prune packet


Basic test to see if multicast is flowing

R5 who is the receiver will ping 239.255.255.6 which is the multicast source. Keep in mind that R5’s mroute table only had the RP mcast info before the ping.

Looking at the capture below which was taken from R2’s e0/0 interface you can see a PIM register message with R5 as the source and R6 as the destination


Verifying mroute table of the source

R6_Source#show 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, E – Extranet,
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,
G – Received BGP C-Mroute, g – Sent BGP C-Mroute,
N – Received BGP Shared-Tree Prune, n – BGP C-Mroute suppressed,
Q – Received BGP S-A Route, q – Sent BGP S-A Route,
V – RD & Vector, v – Vector, p – PIM Joins on route,
x – VxLAN group
Outgoing interface flags: H – Hardware switched, A – Assert winner, p – PIM Join
Timers: Uptime/Expires
Interface state: Interface, Next-Hop or VCD, State/Mode

(*, 239.255.255.6), 01:28:25/stopped, RP 2.2.2.1, flags: SJCL
Incoming interface: Ethernet0/0, RPF nbr 46.1.1.4
Outgoing interface list:
Loopback0, Forward/Sparse, 01:28:25/00:02:09

(51.1.1.5, 239.255.255.6), 01:23:29/00:02:02, flags: LJT
Incoming interface: Ethernet0/0, RPF nbr 46.1.1.4
Outgoing interface list:
Loopback0, Forward/Sparse, 01:23:29/00:02:09

(*, 224.0.1.40), 02:25:21/00:02:42, RP 0.0.0.0, flags: DCL
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
Ethernet0/0, Forward/Sparse, 02:25:19/00:02:42


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