8.14 Auto-RP Listener
• Switch from PIM SM/DM on all interfaces to PIM SM, except for the loopback 0, and Tunnel 0 interfaces.
• Ensure that the S0/0 interface of R1 is not shutdown.
• Ensure all devices still hear Auto-RP announcements.
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Auto-RP listener is another solution designed to allow using Auto-RP without
risking any groups falling back to dense mode forwarding. This feature works in
tandem with PIM sparse mode enabled on all interfaces (not PIM SM/DM).
However, two Auto-RP multicast groups 224.0.1.39 and 224.0.1.40 are flooded in
dense mode. No other groups are allowed to use dense mode and thus
dangerous flooding fallback is eliminated.
R1:
interface FastEthernet 0/0
ip pim sparse-mode
!
interface Serial 0/0.1
ip pim sparse-mode
!
ip pim autorp listener
R3:
interface Serial 1/0.1
ip pim sparse-mode
!
ip pim autorp listener
R4:
interface FastEthernet 0/1
ip pim sparse-mode
!
interface Serial 0/1/0
ip pim sparse-mode
!
ip pim autorp listener
R5:
interface FastEthernet 0/0
ip pim sparse-mode
!
interface Serial 0/0/0
ip pim sparse-mode
!
interface Serial 0/1/0
ip pim sparse-mode
!
ip pim autorp listener
R6:
interface FastEthernet 0/0.146
ip pim sparse-mode
!
ip pim autorp listener
SW2:
interface Vlan 58
ip pim sparse-mode
!
interface Port-Channel 1
ip pim sparse-mode
!
ip pim autorp listener
SW4:
interface Port-Channel 1
ip pim sparse-mode
!
ip pim autorp listener
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Make sure that all transit interfaces are configured for PIM SM. Repeat the
following operation on all routers and pay attention to the Ver/Mode field.
Rack1R5#show ip pim interface
Address Interface Ver/ Nbr Query DR DR
Mode Count Intvl Prior
155.1.58.5 FastEthernet0/0 v2/S 1 30 1 155.1.58.8
155.1.45.5 Serial0/1 v2/S 1 30 1 0.0.0.0
155.1.0.5 Serial0/0 v2/S 2 30 1 155.1.0.5
150.1.5.5 Loopback0 v2/SD 0 30 1 150.1.5.5
Rack1R5#
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Rack1R1#show ip pim autorp
AutoRP Information:
AutoRP is enabled.
AutoRP groups over sparse mode interface is enabled
PIM AutoRP Statistics: Sent/Received
RP Announce: 0/0, RP Discovery: 0/371
Rack1R1#
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Ensure that all routers are still capable of learning Auto-RP information.
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Rack1R6#show ip pim rp mapping
PIM Group-to-RP Mappings
Group(s) 224.0.0.0/5
RP 150.1.8.8 (?), v2v1
Info source: 150.1.5.5 (?), elected via Auto-RP
Uptime: 00:47:21, expires: 00:02:24
Group(s) 224.0.0.0/4
RP 150.1.10.10 (?), v2v1
Info source: 150.1.5.5 (?), elected via Auto-RP
Uptime: 00:48:08, expires: 00:02:23
Group(s) (-)224.110.110.110/32
RP 150.1.8.8 (?), v2v1
Info source: 150.1.5.5 (?), elected via Auto-RP
Uptime: 00:15:29, expires: 00:02:25
Group(s) 232.0.0.0/5
RP 150.1.10.10 (?), v2v1
Info source: 150.1.5.5 (?), elected via Auto-RP
Uptime: 00:44:36, expires: 00:02:25
Rack1R6#
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Check that the Auto-RP groups (224.0.1.39 and 224.0.1.40) are still forwarded
without any RP information. Observe that the output shows Forward/Sparse, but
the actual forwarding uses dense mode.
Rack1R1#show 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
(*, 224.10.10.10), 00:14:52/00:02:33, RP 150.1.8.8, flags: S
Incoming interface: Serial0/0.1, RPF nbr 155.1.0.5
Outgoing interface list:
Tunnel0, Forward/Sparse-Dense, 00:14:52/00:02:33
(*, 239.6.6.6), 00:38:12/00:02:56, RP 150.1.10.10, flags: SJC
Incoming interface: Serial0/0.1, RPF nbr 155.1.0.5
Outgoing interface list:
FastEthernet0/0, Forward/Sparse, 00:38:12/00:02:56
(*, 224.0.1.39), 00:08:44/stopped, RP 0.0.0.0, flags: DC
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
Tunnel0, Forward/Sparse-Dense, 00:08:44/00:00:00
Serial0/0.1, Forward/Sparse, 00:08:44/00:00:00
FastEthernet0/0, Forward/Sparse, 00:08:44/00:00:00
(150.1.8.8, 224.0.1.39), 00:08:27/00:01:37, flags: T
Incoming interface: Serial0/0.1, RPF nbr 155.1.0.5
Outgoing interface list:
FastEthernet0/0, Prune/Sparse, 00:08:24/00:01:45, A
Tunnel0, Forward/Sparse-Dense, 00:00:25/00:00:00
(150.1.10.10, 224.0.1.39), 00:08:45/00:01:20, flags: T
Incoming interface: Serial0/0.1, RPF nbr 155.1.0.5
Outgoing interface list:
FastEthernet0/0, Prune/Sparse, 00:07:40/00:01:26, A
Tunnel0, Forward/Sparse-Dense, 00:00:35/00:00:00
(*, 224.0.1.40), 00:09:07/stopped, RP 0.0.0.0, flags: DCL
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
Tunnel0, Forward/Sparse-Dense, 00:09:07/00:00:00
Serial0/0.1, Forward/Sparse, 00:09:07/00:00:00
FastEthernet0/0, Forward/Sparse, 00:09:07/00:00:00
(150.1.5.5, 224.0.1.40), 00:08:56/00:02:08, flags: LT
Incoming interface: Serial0/0.1, RPF nbr 155.1.0.5
Outgoing interface list:
FastEthernet0/0, Forward/Sparse, 00:08:56/00:00:00, A
Tunnel0, Forward/Sparse-Dense, 00:08:56/00:00:00
Rack1R1#
雖然用Sparese但因為啟動auto-rp listener的關係(讓224.0.1.39與40實質上都是dense mode)，
防止其他沒有在SPARSE-DENSE模式下定義的multicast address，變成dense mode.
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