One or more BSRs need to be configured in the domain using
the global configuration command:
ip pim bsr-candidateinterface-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-candidateinterface-type interface-number [group-listaccess-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-listaccess-list-numbergroup-listaccess-list-number
rp-listaccess-list-number
Standard access list of RP addresses from which Auto-RP
announcements will be accepted.
group-listaccess-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-intervalseconds
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-listaccess-list-number]
kbps
Traffic rate in kilobits per second.
infinity
The specified groups will use the shared-tree.
group-listaccess-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-intervalseconds
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
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.
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