- Multicast is used for one-to-many application. It’s using UDP. For example application using multicast is streaming, IPTV, video on demand etc.
- Multicast use two different ways to distribute data between server and host:
1. Source-based tree. The root or server will distribute to all branches that in multicast group. Source-based tree is identified by (S, G) where S is IP source and G is IP group. It creates optimal path between the server and the hosts, but takes more router resources. Every router must maintain path information fro every server.
2. Shared tree. In shared-based tree have RP (rendezvous point). The server sends traffic only to RP, then the RP will forwards it to hosts belonging to the group. Shared tree is identified by (*, G) where * means any source. Shared tree use less router resources, but can result in suboptimal paths.
- Dense mode use source-based tree.
- In dense mode, router will flood multicast traffic to all router that activate multicast on the interface.
- Any router that doesn’t want to receive it must send a prune message to the server.
- Every 3 minutes, flooding multicast traffic then followed by pruning will happen continuously.
- When activate multicast, need command ‘ip multicast-routing’ in the global config.
Lets do the lab J
Practice makes perfect, right?
R1#
ip multicast-routing ---- > must be activated for multicast routing
!
interface Loopback0
ip address 1.1.1.1 255.255.255.255
ip pim dense-mode
ip ospf 1 area 0
!
interface FastEthernet0/0
ip address 12.12.12.1 255.255.255.0
ip pim dense-mode
ip ospf 1 area 0
R2#
ip multicast-routing
!
interface Loopback0
ip address 2.2.2.2 255.255.255.255
ip pim dense-mode
ip ospf 1 area 0
!
interface FastEthernet0/0
ip address 12.12.12.2 255.255.255.0
ip pim dense-mode
ip ospf 1 area 0
!
interface FastEthernet0/1
ip address 23.23.23.2 255.255.255.0
ip pim dense-mode
ip ospf 1 area 0
R3#
ip multicast-routing
!
interface Loopback0
ip address 3.3.3.3 255.255.255.255
ip pim dense-mode
ip ospf 1 area 0
!
interface FastEthernet0/0
ip address 23.23.23.3 255.255.255.0
ip pim dense-mode
ip ospf 1 area 0
For the testing interface lo0 in R3 will join group to ip multicast for example 239.0.0.1
R3(config-if)#int lo0
R3(config-if)#ip igmp join-group 239.0.0.1
Let’s check ping from R1 to ping ip multicast 239.0.0.1
R1(config-if)#do ping 239.0.0.1
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 239.0.0.1, timeout is 2 seconds:
Reply to request 0 from 23.23.23.3, 168 ms
Reply to request 0 from 23.23.23.3, 220 ms
Let’s check multicast routing table
R3#sh ip mroute interface f0/0
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
(*, 239.0.0.1), 01:45:21/stopped, RP 0.0.0.0, flags: DCL
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
FastEthernet0/0, Forward/Dense, 01:45:21/00:00:00
Loopback0, Forward/Dense, 01:45:21/00:00:00
(*, 224.0.1.40), 01:52:54/00:02:22, RP 0.0.0.0, flags: DCL
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
FastEthernet0/0, Forward/Dense, 01:51:11/00:00:00
Loopback0, Forward/Dense, 01:52:55/00:00:00
R3#sh ip mroute dense
(*, 239.0.0.1), 01:45:39/stopped, RP 0.0.0.0, flags: DCL
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
FastEthernet0/0, Forward/Dense, 01:45:39/00:00:00
Loopback0, Forward/Dense, 01:45:39/00:00:00
(1.1.1.1, 239.0.0.1), 00:00:37/00:02:29, flags: LT
Incoming interface: FastEthernet0/0, RPF nbr 23.23.23.2
Outgoing interface list:
Loopback0, Forward/Dense, 00:00:37/00:00:00
(12.12.12.1, 239.0.0.1), 00:00:37/00:02:29, flags: LT
Incoming interface: FastEthernet0/0, RPF nbr 23.23.23.2
Outgoing interface list:
Loopback0, Forward/Dense, 00:00:37/00:00:00
(*, 224.0.1.40), 01:53:12/00:02:05, RP 0.0.0.0, flags: DCL
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
FastEthernet0/0, Forward/Dense, 01:51:28/00:00:00
Loopback0, Forward/Dense, 01:53:12/00:00:00
R3#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
(*, 239.0.0.1), 01:45:46/stopped, RP 0.0.0.0, flags: DCL
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
FastEthernet0/0, Forward/Dense, 01:45:46/00:00:00
Loopback0, Forward/Dense, 01:45:46/00:00:00
(1.1.1.1, 239.0.0.1), 00:00:45/00:02:21, flags: LT
Incoming interface: FastEthernet0/0, RPF nbr 23.23.23.2
Outgoing interface list:
Loopback0, Forward/Dense, 00:00:46/00:00:00
(12.12.12.1, 239.0.0.1), 00:00:46/00:02:20, flags: LT
Incoming interface: FastEthernet0/0, RPF nbr 23.23.23.2
Outgoing interface list:
Loopback0, Forward/Dense, 00:00:46/00:00:00
(*, 224.0.1.40), 01:53:21/00:02:57, RP 0.0.0.0, flags: DCL
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
FastEthernet0/0, Forward/Dense, 01:51:39/00:00:00
Loopback0, Forward/Dense, 01:53:23/00:00:00
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