- Release 15.4SY Supervisor Engine 2T Software Configuration Guide
- Preface
- Product Overview
- Command-Line Interfaces
- Smart Port Macros
- Virtual Switching Systems (VSS)
- Enhanced Fast Software Upgrade (eFSU)
- Fast Software Upgrades
- Stateful Switchover (SSO)
- Non-Stop Forwarding (NSF)
- RPR Supervisor Engine Redundancy
- Interface Configuration
- UniDirectional Link Detection (UDLD)
- Instant Access
- EnergyWise
- Power Management
- Environmental Monitoring
- Online Diagnostics
- Onboard Failure Logging (OBFL)
- Switch Fabric Functionality
- Cisco IP Phone Support
- Power over Ethernet
- Layer 2 LAN Port Configuration
- Flex Links
- EtherChannels
- IEEE 802.1ak MVRP and MRP
- VLAN Trunking Protocol (VTP)
- VLANs
- Private VLANs (PVLANs)
- Private Hosts
- IEEE 802.1Q Tunneling
- Layer 2 Protocol Tunneling
- Spanning Tree Protocols (STP, MST)
- Optional STP Features
- IP Unicast Layer 3 Switching
- Policy Based Routing (PBR)
- Layer 3 Interface Configuration
- Unidirectional Ethernet (UDE) and unidirectional link routing (UDLR)
- Multiprotocol Label Switching (MPLS)
- MPLS VPN Support
- Ethernet over MPLS (EoMPLS)
- Virtual Private LAN Services (VPLS)
- L2VPN Advanced VPLS (A-VPLS)
- Ethernet Virtual Connections (EVC)
- Layer 2 over Multipoint GRE (L2omGRE)
- Campus Fabric
- IPv4 Multicast Layer 3 Features
- IPv4 Multicast IGMP Snooping
- IPv4 PIM Snooping
- IPv4 Multicast VLAN Registration (MVR)
- IPv4 IGMP Filtering
- IPv4 Router Guard
- IPv4 Multicast VPN Support
- IPv6 Multicast Layer 3 Features
- IPv6 MLD Snooping
- NetFlow Hardware Support
- Call Home
- System Event Archive (SEA)
- Backplane Platform Monitoring
- Local SPAN, RSPAN, and ERSPAN
- SNMP IfIndex Persistence
- Top-N Reports
- Layer 2 Traceroute Utility
- Mini Protocol Analyzer
- PFC QoS Guidelines and Restrictions
- PFC QoS Overview
- PFC QoS Classification, Marking, and Policing
- PFC QoS Policy Based Queueing
- PFC QoS Global and Interface Options
- AutoQoS
- MPLS QoS
- PFC QoS Statistics Data Export
- Cisco IOS ACL Support
- Cisco TrustSec (CTS)
- AutoSecure
- MAC Address-Based Traffic Blocking
- Port ACLs (PACLs)
- VLAN ACLs (VACLs)
- Policy-Based Forwarding (PBF)
- Denial of Service (DoS) Protection
- Configuring IGMP Proxy
- Control Plane Policing (CoPP)
- Dynamic Host Configuration Protocol (DHCP) Snooping
- IP Source Guard
- Dynamic ARP Inspection (DAI)
- Traffic Storm Control
- Unknown Unicast Flood Control
- IEEE 802.1X Port-Based Authentication
- Configuring Web-Based Authentication
- Port Security
- Lawful Intercept
PIM Snooping
- Prerequisites for PIM Snooping
- Restrictions for PIM Snooping
- Information About PIM Snooping
- Default Settings for PIM Snooping
- How to Configure PIM Snooping
Note ● For complete syntax and usage information for the commands used in this chapter, see these publications:
http://www.cisco.com/en/US/products/ps11846/prod_command_reference_list.html
- Cisco IOS Release 15.4SY supports only Ethernet interfaces. Cisco IOS Release 15.4SY does not support any WAN features or commands.
http://www.cisco.com/en/US/products/hw/switches/ps708/tsd_products_support_series_home.html
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Prerequisites for PIM Snooping
Restrictions for PIM Snooping
- Multicast packets are not bridged in a VLAN to local receivers that send IGMP joins when PIM snooping is enabled in the VLAN and IGMP snooping is disabled in the VLAN. ( CSCta03980)
- When you use the PIM-sparse mode (PIM-SM) feature, downstream routers only see traffic if they previously indicated interest through a PIM join or prune message. An upstream router only sees traffic if it was used as an upstream router during the PIM join or prune process.
- Join or prune messages are not flooded on all router ports but are sent only to the port corresponding to the upstream router mentioned in the payload of the join or prune message.
- Directly connected sources are supported for bidirectional PIM groups. Traffic from directly connected sources is forwarded to the designated router and designated forwarder for a VLAN. In some cases, a nondesignated router (NDR) can receive a downstream (S, G) join. For source-only networks, the initial unknown traffic is flooded only to the designated routers and designated forwarders.
- Dense group mode traffic is seen as unknown traffic and is dropped.
- The AUTO-RP groups (224.0.1.39 and 224.0.1.40) are always flooded.
- The switch snoops on designated forwarder election and maintains a list of all designated forwarder routers for various RPs for the VLAN. All traffic is sent to all designated forwarders which ensures that bidirectional functionality works properly.
- PIM snooping and IGMP snooping can be enabled at the same time in a VLAN. Either RGMP or PIM snooping can be enabled in a VLAN but not both.
- Any non-PIMv2 multicast router will receive all traffic.
- You can enable or disable PIM snooping on a per-VLAN basis.
- All mroute and router information is timed out based on the hold-time indicated in the PIM hello and join/prune control packets. All mroute state and neighbor information is maintained per VLAN.
- With Release 15.1(1)SY1 and later releases, IGMP snooping and PIM snooping constrain VPLS multicast traffic.
Information About PIM Snooping
In networks where a Layer 2 switch interconnects several routers, such as an Internet exchange point (IXP), the switch floods IP multicast packets on all multicast router ports by default, even if there are no multicast receivers downstream. With PIM snooping enabled, the switch restricts multicast packets for each IP multicast group to only those multicast router ports that have downstream receivers joined to that group. When you enable PIM snooping, the switch learns which multicast router ports need to receive the multicast traffic within a specific VLAN by listening to the PIM hello messages, PIM join and prune messages, and bidirectional PIM designated forwarder-election messages.
Note To use PIM snooping, you must enable IGMP snooping on the switch. IGMP snooping restricts multicast traffic that exits through the LAN ports to which hosts are connected. IGMP snooping does not restrict traffic that exits through the LAN ports to which one or more multicast routers are connected.
The following illustrations show the flow of traffic and flooding that results in networks without PIM snooping enabled and the flow of traffic and traffic restriction when PIM snooping is enabled.
Figure 47-1 shows the flow of a PIM join message without PIM snooping enabled. In the figure, the switches flood the PIM join message intended for Router B to all connected routers.
Figure 47-1 PIM Join Message Flow without PIM Snooping
Figure 47-2 shows the flow of a PIM join message with PIM snooping enabled. In the figure, the switches restrict the PIM join message and forward it only to the router that needs to receive it (Router B).
Figure 47-2 PIM Join Message Flow with PIM Snooping
Figure 47-3 shows the flow of data traffic without PIM snooping enabled. In the figure, the switches flood the data traffic intended for Router A to all connected routers.
Figure 47-3 Data Traffic Flow without PIM Snooping
Figure 47-4 shows the flow of data traffic with PIM snooping enabled. In the figure, the switches forward the data traffic only to the router that needs to receive it (Router A).
Figure 47-4 Data Traffic Flow with PIM Snooping
Default Settings for PIM Snooping
How to Configure PIM Snooping
- Enabling PIM Snooping Globally
- Enabling PIM Snooping in a VLAN
- Disabling PIM Snooping Designated-Router Flooding
Enabling PIM Snooping Globally
To enable PIM snooping globally, perform this task:
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This example shows how to enable PIM snooping globally and verify the configuration:
Note You do not need to configure an IP address or IP PIM in order to run PIM snooping.
Enabling PIM Snooping in a VLAN
To enable PIM snooping in a VLAN, perform this task:
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This example shows how to enable PIM snooping on VLAN 10 and verify the configuration:
Disabling PIM Snooping Designated-Router Flooding
Note Do not disable designated-router flooding on switches in a Layer 2 broadcast domain that supports multicast sources.
By default, switches that have PIM snooping enabled will flood multicast traffic to the designated router (DR). This method of operation can send unnecessary multicast packets to the designated router. The network must carry the unnecessary traffic, and the designated router must process and drop the unnecessary traffic.
To reduce the traffic sent over the network to the designated router, disable designated-router flooding. With designated-router flooding disabled, PIM snooping only passes to the designated-router traffic that is in multicast groups for which PIM snooping receives an explicit join from the link towards the designated router.
To disable PIM snooping designated-router flooding, perform this task:
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This example shows how to disable PIM snooping designated-router flooding:
http://www.cisco.com/en/US/products/hw/switches/ps708/tsd_products_support_series_home.html
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