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Chapter 7 - Protocol Independent Multicast-Sparse Mode

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

PIM-SM Version 2 RP Selection
One or more BSRs need to be configured in the domain using the global configuration command:
ip pim bsr-candidate interface-type interface-number hash-mask-length [priority]
interface-type interface-number
The address of the specified interface will be used to identify the BSR.
hash-mask-length
Length of the mask (32 bits maximum) that is ANDed with the group address before the hash function is called. All groups with the same seed correspond to the same RP. If the value is 24, then only the first 24 bits of the group address are used. Therefore, one RP can have multiple groups.
priority
Optional. Value from 0 to 255. The BSR candidate with the largest priority is preferred. If BSR candidates have the same priority, the one with the highest IP address is elected as the BSR.
This command causes the router to send Bootstrap messages to PIM neighbors. When a Bootstrap message is received, the priority and address of the message are compared to the previous message. If they are the same, then the message is forwarded. If the received message has a lower priority, or if the priority is the same but the IP address is lower, the message is discarded. Otherwise, the address and priority are cached and the message is forwarded.
After the bootstrap router(s) are configured, then the RP routers are configured using the global command:
ip pim rp-candidate interface-type interface-number [group-list access-list-number]
The address of the specified interface will be used to identify the candidate RP.
Optional. Standard IP access list used to determine the groups that the candidate RP advertises
To configure a candidate RP that will advertise any multicast group starting with 227, the following command can be used:
ip pim rp-candidate serial 1 group-list 51
access-list 51 permit 227.0.0.0 0.255.255.255
The PIM-SM domain can be divided into BSR subdomains with their own configured BSRs. If you do not want BSR messages to cross domains, use the interface configuration command
ip pim border
When this command is used, no Bootstrap messages can pass through the router in either direction, but other PIM messages can pass through the router.
By default, a router will accept all Join and Prune messages. A router can be configured to accept Joins or Prunes for specified groups for a specified RP. The command used to accomplish this filtering is the global command:
ip pim accept-rp {address | auto-rp} [access-list-number]
address
Address of the RP.
auto-rp
Messages are accepted only for RPs that are in the Auto-RP cache.
access-list-number
Optional. Defines the groups that are allowed.
This command causes the router to accept only Join and Prune messages destined for the specified RP. If an access list is used, then the group must also be allowed by the list. If the address in the command is an address on the receiving router, then the router is the RP and it will accept messages only for the groups specified. If the group is not allowed by the access list, then the router will respond immediately to Register messages with Register-Stop messages. For example, to configure a router to accept Join and Prune messages for the RP whose ID is 172.16.1.1 related to groups 225.0.0.0 through 225.255.255.255, use the command
ip pim accept-rp 172.16.1.1 8
access-list 8 permit 225.0.0.0 0.255.255.255
RP mapping agents can be configured to filter Auto-RP announcements using the global configuration command:
ip pim rp-announce-filter rp-list access-list-number group-list access-list-number
rp-list access-list-number
Standard access list of RP addresses from which Auto-RP announcements will be accepted.
group-list access-list-number
Standard access list of group addresses that will be accepted.
For example, to configure an RP mapping agent to accept Auto-RP announcements from the RP with address 172.16.1.1 for all multicast groups, use
ip pim rp-announce-filter rplist 12 group-list 13
access-list 12 permit 172.16.1.1
access-list 13 permit 224.0.0.0 15.255.255.255
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, then the router automatically switches to PIM version 1. If the PIM version 1 neighbors somehow vanish, the router switches the interface back to PIM version 2.
Figure 7-34: Example network for static RP configuration. Only the leaf routers need to be configured with the address of the RP.
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
PIM-SM SPT-Switchover is controlled by the global configuration command:
ip pim spt-threshold {kbps | infinity} [group-list access-list-number]
kbps
Traffic rate in kilobits per second.
infinity
The specified groups will use the shared-tree.
group-list access-list-number
Optional. Determines which groups to apply the threshold.
By default, a PIM-SM router sends periodic Join/Prune messages every 60 seconds. To alter this interval, use the global configuration command
ip pim message-interval seconds
seconds
Value in the range 1 to 65535
All PIM-SM-enabled routers should be configured with the same message interval time. A router will be pruned from a group if a Join message is not received in the message interval. The default value is three minutes.
Example of an PIM-SM Network
The networks that follow will be configured for PIM-SM and each of the RP configuration methods (see Figure 7-34). This network will be used to illustrate complete router configurations and the information that can be gathered using PIM Show and Debug commands.
Network 1 — Static RP Router Configurations
Router A
hostname A
ip multicast-routing
interface Ethernet 0
ip address 172.16.1.1 255.255.255.0
ip pim sparse-mode
interface Serial 0
ip address 172.16.2.1 255.255.255.0
ip pim sparse-mode
clock rate 1540000
interface Serial 1
ip address 172.16.3.1 255.255.255.0
ip pim sparse-mode
clock rate 1540000
router eigrp 100
network 172.16.0.0
ip pim rp-address 172.16.2.2
Router B
hostname B
ip multicast-routing
interface Ethernet 0
ip address 172.16.4.1 255.255.255.0
ip pim sparse-mode
interface Serial 1
ip address 172.16.3.2 255.255.255.0
ip pim sparse-mode
router eigrp 100
network 172.16.0.0
ip pim rp-address 172.16.2.2
Router C
hostname C
ip multicast-routing
interface Ethernet 0
ip address 172.16.4.2 255.255.255.0
ip pim sparse-mode
interface Serial 1
ip address 172.16.5.2 255.255.255.0
ip pim sparse-mode
clock rate 1540000
router eigrp 100
network 172.16.0.0
ip pim rp-address 172.16.2.2
Router RP
hostname RP
ip multicast-routing
interface Serial 0
ip address 172.16.2.2 255.255.255.0
ip pim sparse-mode
interface Serial 1
ip address 172.16.5.1 255.255.255.0
ip pim sparse-mode
router eigrp 100
network 172.16.0.0
Use the command show ip pim rp to verify that the routers have learned the location of the RP.
show ip pim rp [group-name | group-address | mapping]
group-name
Optional. Show RPs for the named group.
group-address
Optional. Show RPs for the group with the entered group address.
mapping
Optional. Display all group to RP mappings.
A#show ip pim rp
Group: 224.0.1.40, RP: 172.16.2.2, next RP-reachable in 00:01:11
The operation of PIM can be verified and monitored using the debug command, debug ip pim.
Aadebug ip pim
PIM debugging is on
08:31:16: PIM: Received v2 Hello on Serial1 from 172.16.2.1
08:31:16: PIM: Received v2 Hello on Serial0 from 172.16.5.2
08:31:16: PIM: Send v2 Hello on Serial0
08:31:26: PIM: Send v2 Hello on Serial1
08:31:30: PIM: Received v2 Join/Prune on Serial1 from 172.16.2.1, to us
08:31:30: PIM: Join-list: (*, 224.0.1.40) RP 172.16.2.2, RPT-bit set, WC-bit set, S-bit set
08:31:30: PIM: Add Serial1/172 .16.2.1 to (*, 224.0.1.40), Forward state
08:31:39: PIM: Received v2 Join/Prune on Serial0 from 172.16.5.2, to us
08:31:39: PIM: Join-list: (*, 224.0.1.40) RP 172.16.2.2, RPT-bit set, WC-bit set, S-bit set
08:31:39: PIM: Add Serial0/172 .16.5.2 to (*, 224.0.1.40), Forward state
08:31:40: PIM: Building Join/Prune message for 224.0.1.40
08:31:46: PIM: Received v2 Hello on Serial1 from 172.16.2.1
08:31:46: PIM: Received v2 Hello on Serial0 from 172.16.5.2
08:31:46: PIM: Send v2 Hello on Serial0
08:31:56: PIM: Send v2 Hello on Serial1
08:32:16: PIM: Received v2 Hello on Serial1 from 172.16.2.1
08:32:16: PIM: Received v2 Hello on Serial0 from 172.16.5.2
08:32:16: PIM: Send v2 Hello on Serial0
Network 2 — Auto-RP Configuration
Auto-RP  Router Configurations
Router MA
hostname MA
ip multicast-routing
interface Ethernet 0
ip address 172.16.1.1 255.255.255.0
ip pim sparse-mode
interface Serial 0
ip address 172.16.2.1 255.255.255.0
ip pim sparse-mode
clock rate 1540000
interface Serial 1
ip address 172.16.3.1 255.255.255.0
ip pim sparse-mode
clock rate 1540000
router eigrp 100
network 172.16.0.0
ip pim send-rp-announce
Router B
hostname B
ip multicast-routing
interface Ethernet 0
ip address 172.16.4.1 255.255.255.0
ip pim sparse-mode
interface Serial 1
ip address 172.16.3.2 255.255.255.0
ip pim sparse-mode
router eigrp 100
network 172.16.0.0
Router C
hostname C
ip multicast-routing
interface Ethernet 0
ip address 172.16.4.2 255.255.255.0
ip pim sparse-mode
interface Serial 1
ip address 172.16.5.2 255.255.255.0
ip pim sparse-mode
clock rate 1540000
router eigrp 100
network 172.16.0.0
Router RP
hostname RP
ip multicast-routing
interface Serial 0
ip address 172.16.2.2 255.255.255.0
ip pim sparse-mode
interface Serial 1
ip address 172.16.5.1 255.255.255.0
ip pim sparse-mode
router eigrp 100
network 172.16.0.0
ip pim send-rp-announce scope 16 group-list 1
access-list 1 permit 224.0.0.0 15.255.255.255
For the network of Figure 7-35, show the RP mappings on the mapping agent and on the RP router.
Figure 7-35: PIM-SM using Auto-RP.
MA#show ip pim rp mapping
PIM Group-to-RP Mappings
This system is an RP-mapping agent
Group(s) 224.0.0.0/4
RP 172.16.5.1 (?), v2v1
  Info source: 172.16.5.1 (?), via Auto-RP
   Uptime: 00:15:06, expires: 00:02:53
RP#show ip pim rp mapping
PIM Group-to-RP Mappings
This system is an RP (Auto-RP)
Group(s) 224.0.0.0/4
RP 172.16.5.1 (?), v2v1
  Info source: 172.16.2.1 (?), via Auto-RP
   Uptime: 00:17:18, expires: 00:02:33
Verify the Auto-RP operation with the debug ip pim:
RP#debug ip pim auto-rp
PIM Auto-RP debugging is on
08:46:19: Auto-RP: Received RP-discovery, from 172.16.2.1, RP_cnt 1, holdtime 18
0 secs
08:46:19: Auto-RP: update (224.0.0.0/4 , RP:172.16.5.1), PIMv2 v1
08:46:19: Auto-RP: Build RP-Announce packet for 172.16.5.1, PIMv2/v1
08:46:19: Auto-RP: Build announce entry for (224.0.0.0/4 )
08:46:19: Auto-RP: Send RP-Announce packet, IP source 172.16.5.1, ttl 16 holdtime 181 secs
08:47:19: Auto-RP: Received RP-discovery, from 172.16.2.1, RP_cnt 1, holdtime 180 secs
08:47:19: Auto-RP: update (224.0.0.0/4 , RP:172.16.5.1), PIMv2 v1
08:47:19: Auto-RP: Build RP-Announce packet for 172.16.5.1, PIMv2/v1
08:47:19: Auto-RP: Build announce entry for (224.0.0.0/4 )
08:47:19: Auto-RP: Send RP-Announce packet, IP source 172.16.5.1, ttl 16 holdtime 181 secs
MA#debug ip pim auto-rp
PIM Auto-RP debugging is on
08:47:53: Auto-RP: Build RP-Discovery packet
08:47:53: Auto-RP: Build mapping (224.0.0.0/4 , RP:172.16.5.1), PIMv2 v1,
08:47:53: Auto-RP: Send RP-discovery packet (1 RP entries)
08:47:53: Auto-RP: Received RP-discovery, from ourselves (172.16.1.1), ignored
08:47:53: Auto-RP: Received RP-announce, from 172.16.5.1, RP_cnt 1, holdtime 181 secs
08:47:53: Auto-RP: update (224.0.0.0/4 , RP:172.16.5.1), PIMv2 v1
08:48:52: Auto-RP: Build RP-Discovery packet
08:48:52: Auto-RP: Build mapping (224.0.0.0/4 , RP:172.16.5.1), PIMv2 v1,
08:48:52: Auto-RP: Send RP-discovery packet (1 RP entries)
08:48:52: Auto-RP: Received RP-discovery, from ourselves (172.16.1.1), ignored
08:48:53: Auto-RP: Received RP-announce, from 172.16.5.1, RP_cnt 1, holdtime 181 secs
08:48:53: Auto-RP: update (224.0.0.0/4 , RP:172.16.5.1), PIMv2 v1
Network 3 — Using Bootstrap Routers
BSR-RP  Router Configurations
Router BSR1
hostname BSR1
ip multicast-routing
interface Ethernet 0
ip address 172.16.1.1 255.255.255.0
ip pim sparse-mode
interface Serial 0
ip address 172.16.2.1 255.255.255.0
ip pim sparse-mode
clock rate 1540000
interface Serial 1
ip address 172.16.3.1 255.255.255.0
ip pim sparse-mode
clock rate 1540000
router eigrp 100
network 172.16.0.0
ip pim bsr-candidate serial 0 24 8
Router RP1
hostname RP1
ip multicast-routing
interface Ethernet 0
ip address 172.16.4.1 255.255.255.0
ip pim sparse-mode
interface Serial 1
ip address 172.16.3.2 255.255.255.0
ip pim sparse-mode
router eigrp 100
network 172.16.0.0
ip pim rp-candidate ethernet 0
Router BSR2
hostname BSR2
ip multicast-routing
interface Ethernet 0
ip address 172.16.4.2 255.255.255.0
ip pim sparse-mode
interface Serial 1
ip address 172.16.5.2 255.255.255.0
ip pim sparse-mode
clock rate 1540000
router eigrp 100
network 172.16.0.0
ip pim bsr-candidate ethernet 0 24 8
Router RP2
hostname RP2
ip multicast-routing
interface Serial 0
ip address 172.16.2.2 255.255.255.0
ip pim sparse-mode
interface Serial 1
ip address 172.16.5.1 255.255.255.0
ip pim sparse-mode
router eigrp 100
network 172.16.0.0
ip pim rp-candidate serial 0
Two candidate Bootstrap routers have been configured in the network of Figure 7-36. Router BSR2 should be elected for this because its IP address is higher than BSR2. To view the BSR, use the show ip pim bsr command.
Figure 7-36: PIM-SM RP selection using Bootstrap routers.
rp1ashow ip pim bsr-router
PIMv2 Bootstrap information
BSR address:172.16.4.2 (?)
Uptime:00:06:46, BSR Priority: 8, Hash mask length: 24
Expires:00:01:43
Next Cand_RP_advertisement in 00:00:35
RP: 172.16.5.1(Serial0)
PIM-SM Bootstrap Border Router  A PIM-SM network can be divided into regions that are serviced by a regional Bootstrap router. Bootstrap messages can then be confined to a region by configuring a border router that does not allow Bootstrap messages from passing through the router, but the router will forward all other PIM traffic. The interface command used to configure a Bootstrap border router is
ip pim border
An example of the use of the border command is shown in Figure 7-37.
Figure 7-37: PIM-SM Bootstrap border router
Border Configuration
interface Serial 0
ip pim sparse-mode
ip pim border
interface Serial 1
ip pim sparse-mode
ip pim border
References
RFC 2362, “Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification,” D. Estrin, D. Farinacci, A. Helmy, D. Thaler, S. Deering, M. Handley, V. Jacobson, C. Liu, P. Sharma, L. Wei, 1998
RFC 2117, “Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification,” D. Estrin, D. Farinacci, A. Helmy, D. Thaler, S. Deering, M. Handley, V. Jacobson, C. Liu, P. Sharma, L. Wei, 1997

 


 
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