CONFIGURING NATIVE MULTICAST

In this post we will use a simple topology and configure Native Multicast step by step and verify the results as well.

configuring-native-multicast

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STEP 1:

Enable ‘ip multicast-routing’ on all routers in global mode.

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STEP 2:

Enable IGP on all the routers an in our case we have enable OSPF process 1 on all routers and area is 0.

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STEP 3:

Next we enable ‘ip pim sparse –mode’ on all interfaces of each router.

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STEP 4:

Now we configure IGMP on R5’s loopback interface to act as receiver.

interface Loopback0ip address 9.9.0.5 255.255.255.255

ip pim sparse-mode

ip igmp join-group 239.192.1.1

ip ospf 1 area 0

We can verify it as well on R5 as below that it has joined the group 239.192.1.1 as below:

R5#sh ip igmp groups

IGMP Connected Group Membership Group Address Interface Uptim ExpiresLast Reporter   Group Accounted

239.192.1.1     Loopback0               00:14:43 00:02:31 9.9.0.5

224.0.1.40      Loopback0               00:14:39 00:02:25 9.9.0.5

We see router has also joined group 224.0.1.40 which is a default multicast group that each router joins to listen to RP discovery messages advertised by mapping agent.Mapping agent on other hand receives the announcement for RP-candidates on group address 224.0.1.39.

STEP 5:

Configure the RP as below using Cisco Proprietary Auto-RP which enables the RP to be discovered dynamically.

(Config)# ip pim send-rp-announce Loopback0 scope 32 >>>>>>To announce itself as RP candidate>

(Config)# ip pim send-rp-discovery Loopback0 scope 32 >>>>>>>Configures the router to be an RP mapping agent.>

As soon as Router R5 joins group 239.192.1.1 it sends IGMPV2 join message.

*Dec 23 01:54:28.923: IGMP(0): Send v2 Report for 239.192.1.1 on Loopback0*

Dec 23 01:54:28.923: IGMP(0): Received v2 Report on Loopback0 from 9.9.0.5 for 239.192.1.1

This JOIN message is then forwarded towards the RP by each router and a (*,G) entry gets created on each router.

R1#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, 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,

Q – Received BGP S-A Route, q – Sent BGP S-A Route,

V – RD & Vector, v – Vector

Outgoing interface flags: H – Hardware switched, A – Assert winner

Timers: Uptime/Expires

Interface state: Interface, Next-Hop or VCD, State/Mode

(*, 239.192.1.1), 00:00:36/00:03:19, RP 9.9.0.3, flags: S

Incoming interface: FastEthernet0/0, RPF nbr 9.9.12.2

Outgoing interface list:

FastEthernet1/1, Forward/Sparse, 00:00:36/00:03:19

 

Same entry is seen to be created on R2 as well:

R2#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, 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,

Q – Received BGP S-A Route, q – Sent BGP S-A Route,

V – RD & Vector, v – Vector

Outgoing interface flags: H – Hardware switched, A – Assert winner

Timers: Uptime/Expires

Interface state: Interface, Next-Hop or VCD, State/Mode

(*, 239.192.1.1), 00:01:08/00:03:20, RP 9.9.0.3, flags: S

Incoming interface: FastEthernet1/0, RPF nbr 9.9.23.3

Outgoing interface list:

FastEthernet0/0, Forward/Sparse, 00:01:08/00:03:20

R3 also has and entry in mroute table for (*,G).

(*, 239.192.1.1), 00:04:00/00:02:37, RP 9.9.0.3, flags: S

Incoming interface: Null, RPF nbr 0.0.0.0

Outgoing interface list:

FastEthernet0/0, Forward/Sparse, 00:02:49/00:02:37

Important to note in R3’s output is that we have Incoming interface as Null as for (*,G) entry incoming interface always leads towards the RP.Contrary outgoing interface leads towards the receiver.

 

STEP 6:

Enable command ‘ip pim autorp listener’ on routers except RP to enable them to dynamically learn about RP.
The “ip pim autorp listener’ allows the Group 224.0.0.39 & 224.0.0.40 to be densed flooded

VERIFICATION:

Now we will try to ping from R6 to group address 239.192.1.1 and we get a reply means the multicast is working
R6#ping 239.192.1.1

Type escape sequence to abort.

Sending 1, 100-byte ICMP Echos to 239.192.1.1, timeout is 2 seconds:

Reply to request 0 from 9.9.0.5, 1308 ms

Reply to request 0 from 9.9.0.5, 1360 ms

R3:

(9.9.0.6, 239.192.1.1), 00:00:03/00:02:56, flags:

Incoming interface: FastEthernet1/0, RPF nbr 9.9.34.3

Outgoing interface list:

FastEthernet0/0, Forward/Sparse, 00:00:03/00:03:26

R2:

(9.9.0.6, 239.192.1.1), 00:00:43/00:02:16, flags: T

Incoming interface: FastEthernet1/0, RPF nbr 9.9.23.3

Outgoing interface list:

FastEthernet0/0, Forward/Sparse, 00:00:43/00:03:18

R1:

(9.9.0.6, 239.192.1.1), 00:00:59/00:02:00, flags: T

Incoming interface: FastEthernet0/0, RPF nbr 9.9.12.2

Outgoing interface list:

FastEthernet1/1, Forward/Sparse, 00:00:59/00:03:29

R5:
(9.9.0.6, 239.192.1.1), 00:01:13/00:01:46, flags: LJT

Incoming interface: FastEthernet0/0, RPF nbr 9.9.15.1

Outgoing interface list:

Loopback0, Forward/Sparse, 00:01:13/00:02:36

Once the Source information is received on the RP in REGISTER MESSAGE from first hop router, the RP sends a JOIN message towards the Source now and builds the Shortest path tree and then RP sends a REGISTER STOP message towards the source to complete registration process.

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