- Information About PIM
- Licensing Requirements for PIM
- Guidelines and Limitations for PIM
- Default Settings
- Configuring PIM
- Enabling the PIM Features
- Configuring PIM Sparse Mode
- Configuring ASM
- Setting the Maximum Number of Entries in the Multicast Routing Table
- Preventing Duplicate Packets During an RPT to SPT Switchover
- Configuring SSM
- Configuring RPF Routes for Multicast
- Configuring Route Maps to Control RP Information Distribution
- Configuring Message Filtering
- Verifying the PIM Configuration
- Displaying Statistics
- Configuration Examples for PIM
- Where to Go Next
- Additional References
- Feature History for PIM
Configuring PIM
This chapter describes how to configure the Protocol Independent Multicast (PIM) features on Cisco NX-OS switches in your IPv4 networks.
Information About PIM
PIM, which is used between multicast-capable routers, advertises group membership across a routing domain by constructing multicast distribution trees. PIM builds shared distribution trees on which packets from multiple sources are forwarded, as well as source distribution trees on which packets from a single source are forwarded. For more information about multicast, see the “Information About Multicast” section.
Cisco NX-OS supports PIM sparse mode for IPv4 networks (PIM). (In PIM sparse mode, multicast traffic is sent only to locations of the network that specifically request it.) You can configure PIM to run simultaneously on a router. You can use PIM global parameters to configure rendezvous points (RPs), message packet filtering, and statistics. You can use PIM interface parameters to enable multicast, identify PIM borders, set the PIM hello message interval, and set the designated router (DR) priority. For more information, see the “Configuring PIM Sparse Mode” section.
Note Cisco NX-OS does not support PIM dense mode.
In Cisco NX-OS, multicast is enabled only after you enable the PIM feature on each router and then enable PIM sparse mode on each interface that you want to participate in multicast. You can configure PIM for an IPv4 network. In an IPv4 network, if you have not already enabled IGMP on the router, PIM enables it automatically. For information about configuring IGMP, see Chapter 2, “Configuring IGMP”.
You use the PIM global configuration parameters to configure the range of multicast group addresses to be handled by each of the two distribution modes:
- Any Source Multicast (ASM) provides discovery of multicast sources. It builds a shared tree between sources and receivers of a multicast group and supports switching over to a source tree when a new receiver is added to a group. ASM mode requires that you configure an RP.
- Single Source Multicast (SSM) builds a source tree originating at the designated router on the LAN segment that receives a request to join a multicast source. SSM mode does not require you to configure RPs. Source discovery must be accomplished through other means.
You can combine the modes to cover different ranges of group addresses. For more information, see the “Configuring PIM” section.
For more information about PIM sparse mode and shared distribution trees used by the ASM mode, see RFC 4601 .
For more information about PIM SSM mode, see RFC 3569 .
Note Multicast equal-cost multipathing (ECMP) is on by default in the Cisco NX-OS for the Cisco Nexus 3000 Series switches; you cannot turn ECMP off. If multiple paths exist for a prefix, PIM selects the path with the lowest administrative distance in the routing table. Cisco NX-OS supports up to 16 paths to a destination.
This section includes the following topics:
- Hello Messages
- Join-Prune Messages
- State Refreshes
- Rendezvous Points
- PIM Register Messages
- Designated Routers
- Administratively Scoped IP Multicast
Hello Messages
The PIM process begins when the router establishes PIM neighbor adjacencies by sending PIM hello messages to the multicast address 224.0.0.13. Hello messages are sent periodically at the interval of 30 seconds. When all neighbors have replied, then the PIM software chooses the router with the highest priority in each LAN segment as the designated router (DR). The DR priority is based on a DR priority value in the PIM hello message. If the DR priority value is not supplied by all routers, or the priorities match, the highest IP address is used to elect the DR.
The hello message also contains a hold-time value, which is typically 3.5 times the hello interval. If this hold time expires without a subsequent hello message from its neighbor, the switch detects a PIM failure on that link.
For added security, you can configure an MD5 hash value that the PIM software uses to authenticate PIM hello messages with PIM neighbors.
Note If PIM is disabled on the switch, the IGMP snooping software processes the PIM hello messages.
For information about configuring hello message authentication, see the “Configuring PIM Sparse Mode” section.
Join-Prune Messages
When the DR receives an IGMP membership report message from a receiver for a new group or source, the DR creates a tree to connect the receiver to the source by sending a PIM join message out the interface toward the rendezvous point (ASM mode) or source (SSM mode).The rendezvous point (RP) is the root of a shared tree, which is used by all sources and hosts in the PIM domain in the ASM mode. SSM does not use an RP but builds a shortest path tree (SPT) that is the lowest cost path between the source and the receiver.
When the DR determines that the last host has left a group or source, it sends a PIM prune message to remove the path from the distribution tree.
The routers forward the join or prune action hop by hop up the multicast distribution tree to create (join) or tear down (prune) the path.
Note In this publication, the terms “PIM join message” and “PIM prune message” are used to simplify the action taken when referring to the PIM join-prune message with only a join or prune action.
Join-prune messages are sent as quickly as possible by the software. You can filter the join-prune messages by defining a routing policy. For information about configuring the join-prune message policy, see the “Configuring PIM Sparse Mode” section.
You can prebuild the SPT for all known (S,G) in the routing table by triggering PIM joins upstream. To prebuild the SPT for all known (S,G)s in the routing table by triggering PIM joins upstream, even in the absence of any receivers, use the ip pim pre-build-spt command. By default, PIM (S,G) joins are triggered upstream only if the OIF-list for the (S,G) is not empty.
State Refreshes
PIM requires that multicast entries are refreshed within a 3.5-minute timeout interval. The state refresh ensures that traffic is delivered only to active listeners, and it keeps routers from using unnecessary resources.
To maintain the PIM state, the last-hop DR sends join-prune messages once per minute. State creation applies to both (*, G) and (S, G) states as follows:
- (*, G) state creation example—An IGMP (*, G) report triggers the DR to send a (*, G) PIM join message toward the RP.
- (S, G) state creation example—An IGMP (S, G) report triggers the DR to send an (S, G) PIM join message toward the source.
If the state is not refreshed, the PIM software tears down the distribution tree by removing the forwarding paths in the multicast outgoing interface list of the upstream routers.
Rendezvous Points
A rendezvous point (RP) is a router that you select in a multicast network domain that acts as a shared root for a multicast shared tree. You can configure as many RPs as you like, and you can configure them to cover different group ranges.
Static RP
You can statically configure an RP for a multicast group range. You must configure the address of the RP on every router in the domain.
You can define static RPs for the following reasons:
For information about configuring static RPs, see the “Configuring Static RPs” section.
BSRs
The bootstrap router (BSR) ensures that all routers in the PIM domain have the same RP cache as the BSR. You can configure the BSR to help you select an RP set from BSR candidate RPs. The function of the BSR is to broadcast the RP set to all routers in the domain. You select one or more candidate BSRs to manage the RPs in the domain. Only one candidate BSR is elected as the BSR for the domain.
Figure 3-1 shows where the BSR mechanism. router A, the software-elected BSR, sends BSR messages out all enabled interfaces (shown by the solid lines in the figure). The messages, which contain the RP set, are flooded hop by hop to all routers in the network. Routers B and C are candidate RPs that send their candidate-RP advertisements directly to the elected BSR (shown by the dashed lines in the figure).
The elected BSR receives candidate-RP messages from all the candidate RPs in the domain. The bootstrap message sent by the BSR includes information about all of the candidate RPs. Each router uses a common algorithm to select the same RP address for a given multicast group.
In the RP selection process, the RP address with the best priority is determined by the software. If the priorities match for two or more RP addresses, the software may use the RP hash in the selection process. Only one RP address is assigned to a group.
By default, routers are not enabled to listen or forward BSR messages. You must enable the BSR listening and forwarding feature so that the BSR mechanism can dynamically inform all routers in the PIM domain of the RP set assigned to multicast group ranges.
Note The BSR mechanism is a nonproprietary method of defining RPs that can be used with third-party routers.
For information about configuring BSRs and candidate RPs, see the “Configuring BSRs” section.
Auto-RP
Auto-RP is a Cisco protocol that was prior to the Internet standard bootstrap router mechanism. You configure Auto-RP by selecting candidate mapping agents and RPs. Candidate RPs send their supported group range in RP-Announce messages to the Cisco RP-Announce multicast group 224.0.1.39. An Auto-RP mapping agent listens for RP-Announce messages from candidate RPs and forms a Group-to-RP mapping table. The mapping agent multicasts the Group-to-RP mapping table in RP-Discovery messages to the Cisco RP-Discovery multicast group 224.0.1.40.
Figure 3-2 shows the Auto-RP mechanism. Periodically, the RP mapping agent multicasts the RP information that it receives to the Cisco-RP-Discovery group 224.0.1.40 (shown by the solid lines in the figure).
By default, routers are not enabled to listen or forward Auto-RP messages. You must enable the Auto-RP listening and forwarding feature so that the Auto-RP mechanism can dynamically inform routers in the PIM domain of the Group-to-RP mapping.
For information about configuring Auto-RP, see the “Configuring Auto-RP” section.
Anycast-RP
Anycast-RP has two implementations: one uses Multicast Source Discovery Protocol (MSDP) and the other is based on RFC 4610 , Anycast-RP Using Protocol Independent Multicast (PIM) . This section describes how to configure PIM Anycast-RP.
You can use PIM Anycast-RP to assign a group of routers, called the Anycast-RP set, to a single RP address that is configured on multiple routers. The set of routers that you configure as Anycast-RPs is called the Anycast-RP set. This method is the only RP method that supports more than one RP per multicast group, which allows you to load balance across all RPs in the set. The Anycast RP supports all multicast groups.
PIM register messages are sent to the closest RP and PIM join-prune messages are sent in the direction of the closest RP as determined by the unicast routing protocols. If one of the RPs goes down, unicast routing ensures these message will be sent in the direction of the next-closest RP.
For more information about PIM Anycast-RP, see RFC 4610.
For information about configuring Anycast-RPs, see the “Configuring a PIM Anycast-RP Set” section.
PIM Register Messages
PIM register messages are unicast to the RP by designated routers (DRs) that are directly connected to multicast sources. The PIM register message has the following functions:
- To notify the RP that a source is actively sending to a multicast group.
- To deliver multicast packets sent by the source to the RP for delivery down the shared tree.
The DR continues to send PIM register messages to the RP until it receives a Register-Stop message from the RP. The RP sends a Register-Stop message in either of the following cases:
- The RP has no receivers for the multicast group being transmitted.
- The RP has joined the SPT to the source but has not started receiving traffic from the source.
You can use the ip pim register-source command to configure the IP source address of register messages when the IP source address of a register message is not a uniquely routed address to which the RP can send packets. This situation might occur if the source address is filtered so that the packets sent to it are not forwarded or if the source address is not unique to the network. In these cases, the replies sent from the RP to the source address fails to reach the DR, resulting in Protocol Independent Multicast sparse mode (PIM-SM) protocol failures.
The following example shows how to configure the IP source address of the register message to the loopback 3 interface of a DR:
Note In Cisco NX-OS, PIM register messages are rate limited to avoid overwhelming the RP.
You can filter PIM register messages by defining a routing policy. For information about configuring the PIM register message policy, see the “Configuring Shared Trees Only for ASM” section.
Designated Routers
In PIM ASM and SSM modes, the software chooses a designated router (DR) from the routers on each network segment. The DR is responsible for forwarding multicast data for specified groups and sources on that segment.
The DR for each LAN segment is determined as described in the “Hello Messages” section.
In ASM mode, the DR is responsible for unicasting PIM register packets to the RP. When a DR receives an IGMP membership report from a directly connected receiver, the shortest path is formed to the RP, which may or may not go through the DR. The result is a shared tree that connects all sources transmitting on the same multicast group to all receivers of that group.
In SSM mode, the DR triggers (*, G) or (S, G) PIM join messages toward the source. The path from the receiver to the source is determined hop by hop. The source must be known to the receiver or the DR.
For information about configuring the DR priority, see the “Configuring PIM Sparse Mode” section.
Administratively Scoped IP Multicast
The administratively scoped IP multicast method allows you to set boundaries on the delivery of multicast data. For more information, see RFC 2365 .
You can configure an interface as a PIM boundary so that PIM messages are not sent out that interface. For information about configuring the domain border parameter, see the “Configuring PIM Sparse Mode” section.
You can use the Auto-RP scope parameter to set a time-to-live (TTL) value. For more information, see the “Configuring Shared Trees Only for ASM” section.
Virtualization Support
You can define multiple virtual routing and forwarding (VRF) instances. For each VRF, independent multicast system resources are maintained, including the MRIB.
You can use the PIM show commands with a VRF argument to provide a context for the information displayed. The default VRF is used if no VRF argument is supplied.
For information about configuring VRFs, see the Cisco Nexus 3000 Series NX-OS Unicast Routing Configuration Guide .
Licensing Requirements for PIM
The following table shows the licensing requirements for this feature:
Guidelines and Limitations for PIM
PIM has the following guidelines and limitations:
- Cisco NX-OS PIM does not interoperate with any version of PIM dense mode or PIM sparse mode version 1.
- Cisco Nexus 3000/3100 vPC secondary does not build the S,G interfaces when there is vPC attached source, vPC attached receiver, PIM-DR is on vPC primary, flow ingresses vPC Primary, and no Remote Peer (RP) is defined for this group.
The traffic must only need to be interVLAN routed on these vPC peers and the PIM state is not required to be built on any other devices for an RP to not have to be defined.
For Cisco Nexus 3000 Series devices, this topology cannot be supported because of the hardware limitation. Cisco Nexus 3000 ASIC does not have the capability to detect the RPF fail packets. As a result, the PIM Asserts cannot be generated on VPC when both primary and secondary have the Output Interface List (OIFL) populated. On Cisco Nexus 3000 Series switches, the incoming PIM join on the VPC Switch Virtual Interface (SVI) is ignored.
- Cisco NX-OS 3000 Series switches do not support per multicast group statistics command from the show forward multicast route command.
- Do not configure both Auto-RP and BSR protocols in the same network.
- Configure candidate RP intervals to a minimum of 15 seconds.
- If a switch is configured with a BSR policy that should prevent it from being elected as the BSR, the switch ignores the policy. This behavior results in the following undesirable conditions:
– If a switch receives a BSM that is permitted by the policy, the switch, which incorrectly elected itself as the BSR, drops that BSM so that routers downstream fail to receive it. Downstream switches correctly filter the BSM from the incorrect BSR so that they do not receive RP information.
– A BSM received by a BSR from a different switch sends a new BSM but ensures that downstream switches do not receive the correct BSM.
Configuring PIM
You can configure PIM for each interface.
Note Cisco NX-OS supports only PIM sparse mode version 2. In this publication, “PIM” refers to PIM sparse mode version 2.
You can configure separate ranges of addresses in the PIM domain using the multicast distribution modes described in Table 3-2 .
To configure PIM, follow these steps:
Step 1 From the multicast distribution modes described in Table 3-2 , select the range of multicast groups that you want to configure in each mode.
Step 2 Enable the PIM features. See the “Enabling the PIM Features” section.
Step 3 Configure PIM sparse mode on each interface that you want to participate in a PIM domain. See the “Configuring PIM Sparse Mode” section.
Step 4 Follow the configuration steps for the multicast distribution modes that you selected in Step 1 as follows:
- For ASM mode, see the “Configuring ASM” section.
- For SSM mode, see the “Configuring SSM” section.
- For RPF routes for multicast, see the “Configuring RPF Routes for Multicast” section.
Step 5 Configure message filtering. See the “Configuring Message Filtering” section.
This section includes the following topics:
- Enabling the PIM Features
- Configuring PIM Sparse Mode
- Configuring ASM
- Configuring SSM
- Configuring RPF Routes for Multicast
- Configuring Route Maps to Control RP Information Distribution
- Configuring Message Filtering
Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.
DETAILED STEPS
Configuring PIM Sparse Mode
You configure PIM sparse mode on every switch interface that you want to participate in a sparse mode domain. You can configure the sparse mode parameters described in Table 3-3 .
Enables listening and forwarding of Auto-RP messages. The default is disabled, which means that the router does not listen or forward Auto-RP messages unless it is configured as a candidate RP or mapping agent. |
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Enables listening and forwarding of BSR messages. The default is disabled, which means that the router does not listen or forward BSR messages unless it is configured as a candidate RP or BSR candidate. |
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Configures the IPv4 register rate limit in packets per second. The range is from 1 to 65,535. The default is no limit. |
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Configures the IPv4 initial holddown period in seconds. This holddown period is the time it takes for the MRIB to come up initially. If you want faster convergence, enter a lower value. The range is from 90 to 210. Specify 0 to disable the holddown period. The default is 210. |
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Sets the designated router (DR) priority that is advertised in PIM hello messages on this interface. On a multi-access network with multiple PIM-enabled routers, the router with the highest DR priority is elected as the DR router. If the priorities match, the software elects the DR with the highest IP address. The DR originates PIM register messages for the directly connected multicast sources and sends PIM join messages toward the rendezvous point (RP) for directly connected receivers. Values range from 1 to 4294967295. The default is 1. |
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Enables an MD5 hash authentication key, or password, in PIM hello messages on the interface so that directly connected neighbors can authenticate each other. The PIM hello messages are IPsec encoded using the Authentication Header (AH) option. You can enter an unencrypted (cleartext) key, or one of these values followed by a space and the MD5 authentication key:
The authentication key can be up to 16 characters. The default is disabled. |
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Configures the interval at which hello messages are sent in milliseconds. The range is from 1 to 4294967295. The default is 30000. |
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Enables the interface to be on the border of a PIM domain so that no bootstrap, candidate-RP, or Auto-RP messages are sent or received on the interface. The default is disabled. |
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Configures which PIM neighbors to become adjacent to based on a route-map policy 1 where you can specify IP addresses to become adjacent to with the match ip address command. If the policy name does not exist, or no IP addresses are configured in a policy, then adjacency is established with all neighbors. The default is to become adjacent with all PIM neighbors. Note We recommend that you should configure this feature only if you are an experienced network administrator. |
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For information about configuring multicast route maps, see the “Configuring Route Maps to Control RP Information Distribution” section.
Note To configure the join-prune policy, see the “Configuring Message Filtering” section.
SUMMARY STEPS
2. (Optional) ip pim auto-rp { listen [ forward ] | forward [ listen ]}
3. (Optional) ip pim bsr { listen [ forward ] | forward [ listen ]}
4. (Optional) show ip pim rp [ ip-prefix ] [ vrf vrf-name | all ]
5. (Optional) ip pim register-rate-limit rate
6. (Optional) [ ip | ipv4 ] routing multicast holddown holddown-period
7. (Optional) show running-configuration pim
11. (Optional) ip pim dr-priority priority
12. (Optional) ip pim hello-authentication ah-md5 auth-key
13. (Optional) ip pim hello-interval interval
15. (Optional) ip pim neighbor-policy policy-name
16. (Optional) show ip pim interface [ interface | brief ] [ vrf vrf-name | all ]
DETAILED STEPS
Configuring ASM
Any Source Multicast (ASM) is a multicast distribution mode that require the use of RPs to act as a shared root between sources and receivers of multicast data.
To configure ASM mode, you configure sparse mode and the RP selection method, where you indicate the distribution mode and assign the range of multicast groups.
Configuring Static RPs
You can configure an RP statically by configuring the RP address on every router that will participate in the PIM domain.
You can specify a route-map policy name that lists the group prefixes to use with the match ip multicast command.
SUMMARY STEPS
2. ip pim rp-address rp-address [ group-list ip-prefix | route-map policy-name ]
3. (Optional) show ip pim group-range [ ip-prefix ] [ vrf vrf-name | all ]
DETAILED STEPS
Configuring BSRs
You configure BSRs by selecting candidate BSRs and RPs.
You can configure a candidate BSR with the arguments described in Table 3-4 .
You can configure a candidate RP with the arguments described in Table 3-5 .
Tip You should choose the candidate BSRs and candidate RPs that have good connectivity to all parts of the PIM domain.
You can configure the same router to be both a BSR and a candidate RP. In a domain with many routers, you can select multiple candidate BSRs and RPs to automatically fail over to alternates if a BSR or an RP fails.
To configure candidate BSRs and RPs, follow these steps:
Step 1 Configure whether each router in the PIM domain should listen and forward BSR messages. A router configured as either a candidate RP or a candidate BSR will automatically listen to and forward all bootstrap router protocol messages, unless an interface is configured with the domain border feature. For more information, see the “Configuring PIM Sparse Mode” section.
Step 2 Select the routers to act as candidate BSRs and RPs.
Step 3 Configure each candidate BSR and candidate RP as described in this section.
Step 4 Configure BSR message filtering. See the “Configuring Message Filtering” section.
SUMMARY STEPS
2. ip pim [ bsr ] bsr-candidate interface [ hash-len hash-length ] [ priority priority ]
3. ip pim [ bsr ] rp-candidate interface group-list ip-prefix [ priority priority ] [ interval interval ]
4. (Optional) show ip pim group-range [ ip-prefix ] [ vrf vrf-name | all ]
DETAILED STEPS
ip pim [ bsr ] bsr-candidate interface [ hash-len hash-length ] [ priority priority ] switch(config)# ip pim bsr-candidate ethernet 2/1 hash-len 24 |
Configures a candidate bootstrap router (BSR). The source IP address used in a bootstrap message is the IP address of the interface. The hash length ranges from 0 to 32 and has a default of 30. The priority ranges from 0 to 255 and has a default of 64. For parameter details, see Table 3-4 . |
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ip pim [ bsr ] rp-candidate interface group-list ip-prefix [ priority priority ] [ interval interval ] switch(config)# ip pim rp-candidate ethernet 2/1 group-list 239.0.0.0/24 |
Configures a candidate RP for BSR. The priority ranges from 0, the highest priority, to 65,535 and has a default of 192. The interval ranges from 1 to 65,535 seconds and has a default of 60. Note We recommend that you configure the candidate RP interval to a minimum of 15 seconds. |
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show ip pim group-range [ ip-prefix ] [ vrf vrf-name | all ] |
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Configuring Auto-RP
You can configure Auto-RP by selecting candidate mapping agents and RPs. You can configure the same router to be both a mapping agent and a candidate RP.
You can configure an Auto-RP mapping agent with the arguments described in Table 3-6 .
Interface type and number used to derive the IP address of the Auto-RP mapping agent used in bootstrap messages. |
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Time-To-Live (TTL) value that represents the maximum number of hops that RP-Discovery messages are forwarded. This value can range from 1 to 255 and has a default of 32. Note See the border domain feature in the “Configuring PIM Sparse Mode” section. |
If you configure multiple Auto-RP mapping agents, only one is elected as the mapping agent for the domain. The elected mapping agent ensures that all candidate RP messages are sent out. All mapping agents receive the candidate RP messages and advertise the same RP cache in their RP-discovery messages.
You can configure a candidate RP with the arguments described in Table 3-7 .
Interface type and number used to derive the IP address of the candidate RP used in Bootstrap messages. |
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Multicast groups handled by this RP. Specified in a prefix format. |
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Time-To-Live (TTL) value that represents the maximum number of hops that RP-Discovery messages are forwarded. This value can range from 1 to 255 and has a default of 32. Note See the border domain feature in the “Configuring PIM Sparse Mode” section. |
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Number of seconds between sending RP-Announce messages. This value can range from 1 to 65,535 and has a default of 60. Note We recommend that you configure the candidate RP interval to a minimum of 15 seconds. |
Tip You should choose mapping agents and candidate RPs that have good connectivity to all parts of the PIM domain.
To configure Auto-RP mapping agents and candidate RPs, follow these steps:
Step 1 For each router in the PIM domain, configure whether that router should listen and forward Auto-RP messages. A router configured as either a candidate RP or an Auto-RP mapping agent will automatically listen to and forward all Auto-RP protocol messages, unless an interface is configured with the domain border feature. For more information, see the “Configuring PIM Sparse Mode” section.
Step 2 Select the routers to act as mapping agents and candidate RPs.
Step 3 Configure each mapping agent and candidate RP as described in this section.
Step 4 Configure Auto-RP message filtering. See the “Configuring Message Filtering” section.
SUMMARY STEPS
2. ip pim { send-rp-discovery | { auto-rp mapping-agent }} interface [ scope ttl ]
3. ip pim { send-rp-announce | { auto-rp rp-candidate }} interface group-list ip-prefix [ scope ttl ] [ interval interval ]
4. (Optional) show ip pim group-range [ ip-prefix ] [ vrf vrf-name | all ]
DETAILED STEPS
ip pim { send-rp-discovery | { auto-rp mapping-agent }} interface [ scope ttl ] |
Configures an Auto-RP mapping agent. The source IP address used in Auto-RP Discovery messages is the IP address of the interface. The default scope is 32. For parameter details, see Table 3-6 . |
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ip pim {send-rp-announce | {auto-rp rp-candidate}} interface group-list ip-prefix [ scope ttl ] [ interval interval ] switch(config)# ip pim auto-rp rp-candidate ethernet 2/1 group-list 239.0.0.0/24 |
Configures an Auto-RP candidate RP. The default scope is 32. The default interval is 60 seconds. By default, the command creates an ASM candidate RP. For parameter details, see Table 3-7 . Note We recommend that you configure the candidate RP interval to a minimum of 15 seconds. |
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show ip pim group-range [ ip-prefix ] [ vrf vrf-name | all ] |
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Configuring a PIM Anycast-RP Set
To configure a PIM Anycast-RP set, follow these steps:
Step 1 Select the routers in the PIM Anycast-RP set.
Step 2 Select an IP address for the PIM Anycast-RP set.
Step 3 Configure each peer RP and local address in the PIM Anycast-RP set as described in this section.
SUMMARY STEPS
5. ip pim anycast-rp anycast-rp-address anycast-rp-peer-address
6. Repeat Step 5 using the same anycast-rp for each peer RP in the RP set
7. (Optional) show ip pim group-range [ ip-prefix ] [ vrf vrf-name | all ]
DETAILED STEPS
Configuring Shared Trees Only for ASM
You can configure shared trees only on the last-hop router for Any Source Multicast (ASM) groups, which means that the router never switches over from the shared tree to the SPT when a receiver joins an active group. You can specify a group range where the use of shared trees is to be enforced with the match ip multicast command. This option does not affect the normal operation of the router when a source tree join-prune message is received.
The default is disabled, which means that the software can switch over to source trees.
Note In ASM mode, only the last-hop router switches from the shared tree to the SPT.
SUMMARY STEPS
2. ip pim use-shared-tree-only group-list policy-name
3. (Optional) show ip pim group-range [ ip-prefix ] [ vrf vrf-name | all ]
DETAILED STEPS
Setting the Maximum Number of Entries in the Multicast Routing Table
You can set the maximum number of entries in the multicast routing table (MRT).
SUMMARY STEPS
2. hardware profile multicast max-limit max-entries
DETAILED STEPS
Preventing Duplicate Packets During an RPT to SPT Switchover
Beginning with Cisco NX-OS Release 5.0(3)U1(2), you can prevent duplicate packets in the hardware when the transition from RPT to SPT is in progress.
Note When you use this command to prevent packet duplication during an RPT to SPT switchover, the switch supports source (S, G) route injections at a rate of only 500 routes every two minutes. The multicast routing table must have 500 entries free for source (S, G) routes.
SUMMARY STEPS
2. hardware profile multicast prefer-source-tree
DETAILED STEPS
Configuring SSM
Source-Specific Multicast (SSM) is a multicast distribution mode where the software on the DR connected to a receiver that is requesting data for a multicast source builds a shortest path tree (SPT) to that source.
On an IPv4 network, a host can request multicast data for a specific source only if it is running IGMPv3 and the DR for that host is running IGMPv3. You will usually enable IGMPv3 when you configure an interface for PIM in the SSM mode. For hosts running IGMPv1 or IGMPv2, you can configure group to source mapping using SSM translation. For more information, see Chapter2, “Configuring IGMP”
You can configure the group range that is used by SSM by specifying values on the command line. By default, the SSM group range for PIM is 232.0.0.0/8.
You can specify a route-map policy name that lists the group prefixes to use with the match ip multicast command.
Note If you want to use the default SSM group range, you do not need to configure the SSM group range.
SUMMARY STEPS
2.
ip pim ssm
{
range
{
ip-prefix
|
none
} |
route-map
policy-name
}
no ip pim ssm
{
range
{
ip-prefix
|
none
} |
route-map
policy-name
}
3. (Optional) show ip pim group-range [ ip-prefix ] [ vrf vrf-name | all ]
DETAILED STEPS
Configuring RPF Routes for Multicast
You can define RPF routes for multicast when you want multicast data to diverge from the unicast traffic path. You can define RPF routes for multicast on border routers to enable reverse path forwarding (RPF) to an external network.
Multicast routes are used not to directly forward traffic but to make RPF checks. RPF routes for multicast cannot be redistributed. For more information about multicast forwarding, see the “Multicast Forwarding” section.
SUMMARY STEPS
2. ip mroute { ip-addr mask | ip-prefix } { next-hop | nh-prefix | interface } [ route-preference ] [ vrf vrf-name ]
DETAILED STEPS
Disabling Multicast Multipath
By default, the RPF interface for multicast is chosen automatically when there are multiple ECMP paths available. Disabling the automatic selection allows you to specify a single RPF interface for multicast.
SUMMARY STEPS
2. ip multicast multipath none
3. clear ip mroute * vrf [vrf-name | all | default | management]
Configuring Route Maps to Control RP Information Distribution
You can configure route maps to help protect against some RP configuration errors and malicious attacks. You use route maps in commands that are described in the “Configuring Message Filtering” section.
By configuring route maps, you can control distribution of RP information that is distributed throughout the network. You specify the BSRs or mapping agents to be listened to on each client router and the list of candidate RPs to be advertised (listened to) on each BSR and mapping agent to ensure that what is advertised is what you expect.
Note Only the match ip multicast command has an effect in the route map.
SUMMARY STEPS
2. route-map map-name [ permit | deny ] [ sequence-number ]
3. match ip multicast {{ rp ip-address [ rp-type rp-type ] [ group ip-prefix ]} | { group ip-prefix [ rp ip-address [ rp-type rp-type ]]}
DETAILED STEPS
Configuring Message Filtering
You can configure filtering of the PIM messages described in Table 3-8 .
Enables syslog messages that list the neighbor state changes to be generated. The default is disabled. |
|
Enables PIM register messages to be filtered based on a route-map policy 2 where you can specify group or group and source addresses with the match ip multicast command. This policy applies to routers that act as an RP. The default is disabled, which means that the software does not filter PIM register messages. |
|
Enables BSR candidate RP messages to be filtered by the router based on a route-map policy 1 where you can specify the RP and group addresses, and the type ASM with the match ip multicast command. This command can be used on routers that are eligible for BSR election. The default is no filtering of BSR messages. |
|
Enables BSR messages to be filtered by the BSR client routers based on a route-map policy 1 where you can specify BSR source addresses with the match ip multicast command. This command can be used on client routers that listen to BSR messages. The default is no filtering of BSR messages. |
|
Enables Auto-RP announce messages to be filtered by the Auto-RP mapping agents based on a route-map policy 1 where you can specify the RP and group addresses, and the type ASM with the match ip multicast command. This command can be used on a mapping agent. The default is no filtering of Auto-RP messages. |
|
Enables Auto-RP discover messages to be filtered by client routers based on a route-map policy 1 where you can specify mapping agent source addresses with the match ip multicast command. This command can be used on client routers that listen to discover messages. The default is no filtering of Auto-RP messages. |
|
Enables join-prune messages to be filtered based on a route-map policy 1 where you can specify group, group and source, or group and RP addresses with the match ip multicast command. The default is no filtering of join-prune messages. |
|
For information about configuring multicast route maps, see the “Configuring Route Maps to Control RP Information Distribution” section.
SUMMARY STEPS
2. (Optional) ip pim log-neighbor-changes
3. (Optional) ip pim register-policy policy-name
4. (Optional) ip pim bsr rp-candidate-policy policy-name
5. (Optional) ip pim bsr bsr-policy policy-name
6. (Optional) ip pim auto-rp rp-candidate-policy policy-name
7. (Optional) ip pim auto-rp mapping-agent-policy policy-name
DETAILED STEPS
When routes are flushed, they are removed from the Multicast Routing Information Base (MRIB) and the Multicast Forwarding Information Base (MFIB).
When you restart PIM, the following tasks are performed:
- The PIM database is deleted.
- The MRIB and MFIB are unaffected and forwarding of traffic continues.
- The multicast route ownership is verified through the MRIB.
- Periodic PIM join and prune messages from neighbors are used to repopulate the database.
Note To set the interval for multicast routes to be programmed into the hardware, use the hardware profile multicast soak-interval command. For more information, see Setting Interval for Multicast Routes.
Verifying the PIM Configuration
To display the PIM configuration information, perform one of the following tasks:
For detailed information about the fields in the output from these commands, see the Cisco Nexus 3000 Series Command Reference, .
Displaying Statistics
You can display and clear PIM statistics by using the commands in this section.
This section has the following topics:
Displaying PIM Statistics
You can display the PIM statistics and memory usage using the commands listed in Table 3-9 . Use the show ip form of the command for PIM.
For detailed information about the fields in the output from these commands, see the Cisco Nexus 3000 Series Command Reference, .
Clearing PIM Statistics
You can clear the PIM statistics using the commands listed in Table 3-10 . Use the show ip form of the command for PIM.
Configuration Examples for PIM
This section describes how to configure PIM using different data distribution modes and RP selection methods.
This section includes the following topics:
- Configuration Example for SSM
- Configuration Example for BSR
- Configuration Example for PIM Anycast-RP
Configuration Example for SSM
To configure PIM in SSM mode, follow these steps for each router in the PIM domain:
Step 1 Configure PIM sparse mode parameters on the interfaces that you want to participate in the domain. We recommend that you enable PIM on all interfaces.
Step 2 Configure the parameters for IGMP that support SSM. See Chapter 2, “Configuring IGMP” Usually, you configure IGMPv3 on PIM interfaces to support SSM.
Step 3 Configure the SSM range if you do not want to use the default range.
Step 4 Configure message filtering.
Configuration Example for BSR
To configure PIM in ASM mode using the BSR mechanism, follow these steps for each router in the PIM domain:
Step 1 Configure PIM sparse mode parameters on the interfaces that you want to participate in the domain. We recommend that you enable PIM on all interfaces.
Step 2 Configure whether that router should listen and forward BSR messages.
Step 3 Configure the BSR parameters for each router that you want to act as a BSR.
Step 4 Configure the RP parameters for each router that you want to act as a candidate RP.
Step 5 Configure message filtering.
This example shows how to configure PIM ASM mode using the BSR mechanism and how to configure the BSR and RP on the same router:
Configuration Example for PIM Anycast-RP
To configure ASM mode using the PIM Anycast-RP method, follow these steps for each router in the PIM domain:
Step 1 Configure PIM sparse mode parameters on the interfaces that you want to participate in the domain. We recommend that you enable PIM on all interfaces.
Step 2 Configure the RP address that you configure on all routers in the Anycast-RP set.
Step 3 Configure a loopback with an address to use in communication between routers in the Anycast-RP set for each router that you want to be in the Anycast-RP set.
Step 4 Configure the RP-address which will be used as Anycast-RP on all routers.
Step 5 Configure the Anycast-RP parameters and repeat with the IP address of each Anycast-RP for each router that you want to be in the Anycast-RP set. This example shows two Anycast-RPs.
Step 6 Configure message filtering.
This example shows how to configure PIM ASM mode using two Anycast-RPs:
Additional References
For additional information related to implementing PIM, see the following sections:
MIBs
To locate and download MIBs, go to the following URL: http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml |
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