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Chapter 6 - Protocol Independent Multicast - Dense Mode

Cisco Multicast Routing & Switching
William R. Parkhurst
  Copyright © 1999 The McGraw-Hill Companies

PIM-DM Router Configuration
Configuring PIM-DM on Cisco routers is a relatively simple exercise.
Figure 6-32: Basic PIM-DM router configuration
The first step is to enable multicast routing in global configuration mode using the command:
ip multicast-routing
Next, enable PIM-DM on the router interfaces using the interface command:
ip pim dense-mode
The router in Figure 6-32 has a basic configuration shown in the diagram. Although the configuration has EIGRP as the routing protocol, any of the IP routing protocols could have been used.
The PIM version can be configured using the interface configuration command:
ip pim version [1 | 2]
If an interface is configured for version 2 (the default) and a PIM version 1 neighbor is discovered on the interface, the router will automatically switch to PIM version 1. If the PIM version 1 neighbors somehow go away, the router will switch the interface back to PIM version 2.
The default interval for PIM query messages is 30 seconds. This can be adjusted using the interface command:
ip pim query-interval seconds
seconds
1—65535 seconds
The following command changes the PIM query interval to 60 seconds.
interface Serial 0
ip pim query-interval 60
Monitoring and Debugging PIM Dense Mode
The network in Figure 6-33 is configured with PIM-DM and will be used to demonstrate the PIM show and debug commands. The configurations for the routers in Figure 6-33 are listed on the following page.
Figure 6-33: The network used to demonstrate PIM-DM show and debug commands
Router A
ip multicast-routing
interface Ethernet 0
ip address 172.16.1.1 255.255.255.0
ip pim dense-mode
interface Serial 0
ip address 172.16.2.1 255.255.255.0
clock rate 1540000
ip pim dense-mode
interface Serial 1
ip address 172.16.3.1 255.255.255.0
clock rate 1540000
ip pim dense-mode
router eigrp 100
network 172.16.0.0
Router B
ip multicast-routing
interface Ethernet 0
ip address 172.16.4.1 255.255.255.0
ip pim dense-mode
interface Serial 1
ip address 172.16.3.2 255.255.255.0
clock rate 1540000
ip pim dense-mode
router eigrp 100
network 172.16.0.0
Router C
ip multicast-routing
interface Serial 0
ip address 172.16.2.2 255.255.255.0
ip pim dense-mode
interface Serial 1
ip address 172.16.5.1 255.255.255.0
clock rate 1540000
ip pim dense-mode
router eigrp 100
network 172.16.0.0
Router D
ip multicast-routing
interface Ethernet 0
ip address 172.16.4.2 255.255.255.0
ip pim dense-mode
interface Serial 1
ip address 176.16.5.2 255.255.255.0
clock rate 1540000
ip pim dense-mode
router eigrp 100
network 172.16.0.0
Use the EXEC command show ip pim neighbor to view the state of the PIM interfaces on the routers.
Bashow ip pim neighbor
PIM Neighbor Table
Neighbor Address
Interface
Uptime
Expires
Ver
Mode
172.16.3.1
Serial 1
00:09:40
00:01:35
v2
Dense
172.16.4.2
Ethernet0
00:41:57
00:01:19
v2
Dense (DR)
The fields in the neighbor address are described below.
Neighbor address
IP Address of the PIM neighbor.
Interface
Interface on which the neighbor is attached.
Uptime
How long in hours, minutes, and seconds the neighbor has been in the PIM neighbor table.
Expires
Time to elapse before the neighbor is removed from the table in hours, minutes, and seconds.
Mode
PIM mode of the interface.
(DR)
The neighbor is the designated router on a multi-access network.
The state of a PIM interface can be displayed using the show ip pim interface command.
show ip pim interface [interface-type interface-number] [count]
interface-type
interface-number
Optional. Type and number of the interface (Ethernet 0, Serial 1, etc.)
Optional. Number of packets that have been sent and received on the interface
B4ashow ip pim interface
Address
Interface
Version/Mode
Nbr Count
Query Intvl
DR
172.16.4.2
Ethernet0
v2/Dense
1
30
172.16.4.1
172.16.3.1
Serial1
v2/Dense
1
30
0.0.0.0
Address
IP address of the next hop router.
Interface
PIM interface type and number.
Version/Mode
Configured PIM mode and version number for the interface.
Neighbor Count
Number of discovered PIM neighbors on this interface.
Query Intvl
Configured PIM query interval.
DR
Address of the designated router. Serial interfaces do not have a designated router so this field is set to 0.0.0.0.
B#show ip pim interface count
Address
Interface
FS
Mpackets In/Out
172.16.4.2
Ethernet0
*
686/0
172.16.3.1
Serial1
*
738/0
FS
* indicates that fast switching is enabled
Mpackets In/Out
Number of multicast packets sent or received on the interface.
The operation of PIM can be verified by executing the debug ip pim command:
Badebug ip pim
PIM debugging is on:
B#
08:18:03: PIM: Send v2 Hello on Ethernet0
08:18:06: PIM: Received v2 Hello on Ethernet0 from 172.16.4.2
08:18:10: PIM: Received v2 Hello on Serial1 from 172.16.3.1
08:18:16: PIM: Send v2 Hello on Serial1
08:18:33: PIM: Send v2 Hello on Ethernet0
08:18:36: PIM: Received v2 Hello on Ethernet0 from 172.16.4.2
08:18:40: PIM: Received v2 Hello on Serial1 from 172.16.3.1
08:18:46: PIM: Send v2 Hello on Serial1
Notice that PIM queries to or from a particular neighbor are 30 seconds apart. This is the default query interval for PIM.
References
IETF draft, “Protocol Independent Multicast Version 2 Dense Mode Specification,” S. Deering et. al., 1998, draft-ietf-pim-v2-dm-01.txt

 


 
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