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Table Of Contents
Prerequisites for Configuring Multicast VPN
Restrictions for Configuring Multicast VPN
Information About Configuring Multicast VPN
Multicast VPN Routing and Forwarding and Multicast Domains
Multicast Distributed Switching Support for Multicast VPN
MDT Address Family in BGP for Multicast VPN
BGP Advertisement Methods for Multicast VPN Support
Auto-Migration to the MDT SAFI
Guidelines for Configuring the MDT SAFI
Guidelines for Upgrading a Network to Support the MDT SAFI
How to Configure Multicast VPN
Configuring a Default MDT Group for a VRF
Configuring the MDT Address Family in BGP for Multicast VPN
Configuring the Data Multicast Group
Configuring Multicast Routes and Information
Verifying Information for the MDT Default Group
Configuration Examples for Multicast VPN
Configuring MVPN and SSM: Example
Enabling a VPN for Multicast Routing: Example
Configuring the MDT Address Family in BGP for Multicast VPN: Example
Configuring the Multicast Group Address Range for Data MDT Groups: Example
Configuring the IP Source Address of Register Messages: Example
Configuring an MSDP Peer: Example
Limiting the Number of Multicast Routes: Example
Feature Information for Configuring Multicast VPN
Configuring Multicast VPN
First Published: May 2, 2005Last Updated: July 30, 2010The Multicast VPN (MVPN) feature provides the ability to support multicast over a Layer 3 Virtual Private Network (VPN). As enterprises extend the reach of their multicast applications, service providers can accommodate these enterprises over their Multiprotocol Label Switching (MPLS) core network. IP multicast is used to stream video, voice, and data to an MPLS VPN network core.
Historically, point-to-point tunnels were the only way to connect through a service provider network. Although such tunneled networks tend to have scalability issues, they represented the only means of passing IP multicast traffic through a VPN.
Because Layer 3 VPNs support only unicast traffic connectivity, deploying in conjunction with a Layer 3 VPN allows service providers to offer both unicast and multicast connectivity to Layer 3 VPN customers.
Finding Feature Information in This Module
Your Cisco IOS software release may not support all of the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To reach links to specific feature documentation in this module and to see a list of the releases in which each feature is supported, use the "Feature Information for Configuring Multicast VPN" section.
Finding Support Information for Platforms and Cisco IOS and Catalyst OS Software Images
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
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Prerequisites for Configuring Multicast VPN
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Prerequisites for Configuring Multicast VPN
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Restrictions for Configuring Multicast VPN
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Information About Configuring Multicast VPN
Before you configure MVPN, you should understand the following concepts:
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Multicast VPN Operation
MVPN IP allows a service provider to configure and support multicast traffic in a Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) environment. This feature supports routing and forwarding of multicast packets for each individual VPN routing and forwarding (VRF) instance, and it also provides a mechanism to transport VPN multicast packets across the service provider backbone.
A VPN is network connectivity across a shared infrastructure, such as an Internet service provider (ISP). Its function is to provide the same policies and performance as a private network, at a reduced cost of ownership, thus creating many opportunities for cost savings through operations and infrastructure.
An MVPN allows an enterprise to transparently interconnect its private network across the network backbone of a service provider. The use of an MVPN to interconnect an enterprise network in this way does not change the way that enterprise network is administered, nor does it change general enterprise connectivity.
Benefits of Multicast VPN
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Multicast VPN Routing and Forwarding and Multicast Domains
MVPN introduces multicast routing information to the VPN routing and forwarding table. When a provider edge (PE) router receives multicast data or control packets from a customer edge (CE) router, forwarding is performed according to the information in the Multicast VPN routing and forwarding instance (MVRF). MVPN does not use label switching.
A set of MVRFs that can send multicast traffic to each other constitutes a multicast domain. For example, the multicast domain for a customer that wanted to send certain types of multicast traffic to all global employees would consist of all CE routers associated with that enterprise.
Multicast Distribution Trees
MVPN establishes a static default MDT for each multicast domain. The default MDT defines the path used by PE routers to send multicast data and control messages to every other PE router in the multicast domain.
If Source Specific Multicast (SSM) is used as the core multicast routing protocol, then the multicast IP addresses used for the default and data multicast distribution tree (MDT) must be configured within the SSM range on all PE and P routers.
MVPN also supports the dynamic creation of MDTs for high-bandwidth transmission. Data MDTs are a feature unique to Cisco IOS software. Data MDTs are intended for high-bandwidth sources such as full-motion video inside the VPN to ensure optimal traffic forwarding in the MPLS VPN core. The threshold at which the data MDT is created can be configured on a per-router or a per-VRF basis. When the multicast transmission exceeds the defined threshold, the sending PE router creates the data MDT and sends a User Datagram Protocol (UDP) message, which contains information about the data MDT to all routers on the default MDT. The statistics to determine whether a multicast stream has exceeded the data MDT threshold are examined once every second; on distributed platforms such as the Cisco 7500 and Cisco 12000, those statistics are updated to the route processor every 10 seconds. After a PE router sends the UDP message, it waits 3 more seconds before switching over; 13 seconds is the worst case switchover time; 3 seconds is the best case.
Data MDTs are created only for (S, G) multicast route entries within the VRF multicast routing table. They are not created for (*, G) entries regardless of the value of the individual source data rate.
In the following example, a service provider has a multicast customer with offices in San Jose, New York, and Dallas. A one-way multicast presentation is occurring in San Jose. The service provider network supports all three sites associated with this customer, in addition to the Houston site of a different enterprise customer.
The default MDT for the enterprise customer consists of provider routers P1, P2, and P3 and their associated PE routers. PE4 is not part of the default MDT, because it is associated with a different customer. Figure 1 shows that no data flows along the default MDT, because no one outside of San Jose has joined the multicast.
Figure 1 Default Multicast Distribution Tree Overview
An employee in New York joins the multicast session. The PE router associated with the New York site sends a join request that flows across the default MDT for the multicast domain of the customer. PE1, the PE router associated with the multicast session source, receives the request. Figure 2 depicts that the PE router forwards the request to the CE router associated with the multicast source (CE1a).
Figure 2 Initializing the Data MDT
The CE router (CE1a) begins to send the multicast data to the associated PE router (PE1), which sends the multicast data along the default MDT. Immediately sending the multicast data, PE1 recognizes that the multicast data exceeds the bandwidth threshold for which a data MDT should be created. Therefore, PE1 creates a data MDT, sends a message to all routers using the default MDT that contains information about the data MDT, and, three seconds later, begins sending the multicast data for that particular stream using the data MDT. Only PE2 has interested receivers for this source, so only PE2 will join the data MDT and receive traffic on it.
PE routers maintain a PIM relationship with other PE routers over the default MDT as well as a PIM relationship with its directly attached PE routers.
Multicast Tunnel Interface
An MVRF, which is created per multicast domain, requires the router to create a tunnel interface from which all MVRF traffic is sourced. A multicast tunnel interface is an interface the MVRF uses to access the multicast domain. It can be thought of as a conduit that connects an MVRF and the global MVRF. One tunnel interface is created per MVRF.
Multicast Distributed Switching Support for Multicast VPN
Multicast distributed switching (MDS) is supported for MVPN on the Cisco 7500 series routers. When MDS is configured, ensure that all interfaces enabled for IP multicast have MDS enabled correctly—verify that no interface has the no ip mroute-cache command configured (including loopback interfaces).
MDT Address Family in BGP for Multicast VPN
The mdt keyword has been added to the address-family ipv4 command to configure an MDT address-family session. MDT address-family sessions are used to pass the source PE address and MDT group address to PIM using Border Gateway Protocol (BGP) MDT Subaddress Family Identifier (SAFI) updates.
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BGP Advertisement Methods for Multicast VPN Support
In a single autonomous system, if the default MDT for an MVPN is using PIM sparse mode (PIM-SM) with a rendezvous point (RP), then PIM is able to establish adjacencies over the Multicast Tunnel Interface (MTI) because the source PE and receiver PE discover each other through the RP. In this scenario, the local PE (the source PE) sends register messages to the RP, which then builds a shortest-path tree (SPT) toward the source PE. The remote PE, which acts as a receiver for the MDT multicast group, then sends (*, G) joins toward the RP and joins the distribution tree for that group.
However, if the default MDT group is configured in a PIM Source Specific Multicast (PIM-SSM) environment rather than a PIM-SM environment, the receiver PE needs information about the source PE and the default MDT group. This information is used to send (S, G) joins toward the source PE to build a distribution tree from the source PE (without the need for an RP). The source PE address and default MDT group address are sent using BGP.
Table 1 lists the BGP advertisement methods for sending the source PE address and the default MDT group that are available (by Cisco IOS release).
BGP Extended Community
When BGP extended communities are used, the PE loopback (source address) information is sent as a VPNv4 prefix using Route Distinguisher (RD) Type 2 (to distinguish it from unicast VPNv4 prefixes). The MDT group address is carried in a BGP extended community. Using a combination of the embedded source in the VPNv4 address and the group in the extended community, PE routers in the same MVRF instance can establish SSM trees to each other.
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BGP MDT SAFI
In Cisco IOS releases that support the MDT SAFI, the source PE address and the MDT group address are passed to PIM using BGP MDT SAFI updates. The RD type has changed to RD type 0 and BGP determines the best path for the MDT updates before passing the information to PIM.
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In Cisco IOS releases that support the MDT SAFI, the MDT SAFI address family needs to be explicitly configured for BGP neighbors using the address-family ipv4 mdt command. Neighbors that do not support the MDT SAFI still need to be enabled for the MDT SAFI in the local BGP configuration. Prior to the introduction of the MDT SAFI, additional BGP configuration from the VPNv4 unicast configuration was not needed to support MVPN.
Because the new MDT SAFI does not use BGP route-target extended communities, the regular extended community methods to filter these updates no longer apply. As a result, the match mdt-group route-map configuration command has been added to filter on the MDT group address using access control lists (ACLs). These route maps can be applied—inbound or outbound—to the IPv4 MDT address-family neighbor configuration.
Auto-Migration to the MDT SAFI
In Cisco IOS Release 12.0(30)S3, auto-migration to the MDT SAFI functionality was introduced to ease the migration to the MDT SAFI. This functionality was integrated into Cisco IOS Releases 12.2(33)SRA1, 12.2(31)SB2, and 12.2(33)SXH. When migrating a Cisco IOS release to the MDT SAFI, existing VPNv4 neighbors will be automatically configured for the MDT SAFI upon bootup based on the presence of an existing default MDT configuration (that is, pre-MDT SAFI configurations will be automatically converted to an MDT SAFI configuration upon bootup). In addition, when a default MDT configuration exists and a VPNv4 neighbor in BGP is configured, a similar neighbor in the IPv4 MDT address family will be automatically configured.
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Guidelines for Configuring the MDT SAFI
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Guidelines for Upgrading a Network to Support the MDT SAFI
When moving from a pre-MDT SAFI to an MDT SAFI environment, upmost care should be taken to minimize the impact to the MVPN service. The unicast service will not be affected, other than the outage due to the reload and recovery. To upgrade a network to support the MDT SAFI, we recommended that you perform the following steps:
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Supported Policy
The following policy configuration parameters are supported under the MDT SAFI:
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How to Configure Multicast VPN
This section contains the following procedures.
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Configuring a Default MDT Group for a VRF
Perform this task to configure a default MDT group for a VRF.
The default MDT group must be the same group configured on all routers that belong to the same VPN. The source IP address will be the address used to source the BGP sessions.
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Configuring the MDT Address Family in BGP for Multicast VPN
Perform this task to configure an MDT address family session on PE routers to establish MDT peering sessions for MVPN.
Prerequisites
Before MVPN peering can be established through an MDT address family, MPLS and Cisco Express Forwarding (CEF) must be configured in the BGP network and multiprotocol BGP on PE routers that provide VPN services to CE routers.
Restrictions
The following policy configuration parameters are not supported:
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Configuring the Data Multicast Group
Perform this task to configure a data MDT group.
A data MDT group can include a maximum of 256 multicast groups per VPN per VRF per PE router. Multicast groups used to create the data MDT group are dynamically chosen from a pool of configured IP addresses.
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Configuring Multicast Routes and Information
Perform this task to limit the number of multicast routes that can be added in a router.
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Verifying Information for the MDT Default Group
Perform this task to verify information about the MDT default group.
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DETAILED STEPS
Step 1
Enables privileged EXEC mode.
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Example:Router> enable
Step 2
Enter the show ip msdp peer command to verify detailed information about MSDP peer 224.135.250.116:
Router# show ip msdp peer 224.135.250.116MSDP Peer 224.135.250.116 (rtp5-rp1.cisco.com), AS 109 (configured AS)Description:Connection status:State: Up, Resets: 9, Connection source: Loopback2 (228.69.199.17)Uptime(Downtime): 1d10h, Messages sent/received: 436765/429062Output messages discarded: 0Connection and counters cleared 1w2d agoSA Filtering:Input (S,G) filter: none, route-map: noneInput RP filter: none, route-map: noneOutput (S,G) filter: none, route-map: noneOutput RP filter: none, route-map: noneSA-Requests:Input filter: noneSending SA-Requests to peer: disabledPeer ttl threshold: 0SAs learned from this peer: 32, SAs limit: 500Input queue size: 0, Output queue size: 0Step 3
Enter the show ip msdp summary command to display MSDP peer status:
Router# show ip msdp summaryMSDP Peer Status SummaryPeer Address AS State Uptime/ Reset SA Peer NameDowntime Count Count224.135.250.116 109 Up 1d10h 9 111 rtp5-rp1*144.228.240.253 1239 Up 14:24:00 5 4010 sl-rp-stk172.16.253.19 109 Up 12:36:17 5 10 rtp4-rp1172.16.170.110 109 Up 1d11h 9 12 ams-rp1Step 4
To display information about and to verify information about the BGP advertisement of the route distinguisher (RD) for the MDT default group, use the show ip pim mdt bgp command in EXEC mode.
Router# show ip pim mdt bgp MDT-default group 232.2.1.4 rid:1.1.1.1 next_hop:1.1.1.1Step 5
To display detailed information about and to verify information regarding the MDT data group, perform the following steps.
Enter the show ip pim mdt send command to show the MDT advertisements that a specified router has made.
Router# show ip pim mdt sendMDT-data send list for VRF:vpn8(source, group) MDT-data group ref_count(10.100.8.10, 225.1.8.1) 232.2.8.0 1(10.100.8.10, 225.1.8.2) 232.2.8.1 1(10.100.8.10, 225.1.8.3) 232.2.8.2 1(10.100.8.10, 225.1.8.4) 232.2.8.3 1(10.100.8.10, 225.1.8.5) 232.2.8.4 1(10.100.8.10, 225.1.8.6) 232.2.8.5 1(10.100.8.10, 225.1.8.7) 232.2.8.6 1(10.100.8.10, 225.1.8.8) 232.2.8.7 1(10.100.8.10, 225.1.8.9) 232.2.8.8 1(10.100.8.10, 225.1.8.10) 232.2.8.9 1Step 6
Enter the show ip pim mdt history command to display the data MDTs that have been reused during the past configured interval.
Router# show ip pim vrf vrf1 mdt history interval 20MDT-data send history for VRF - vrf1 for the past 20 minutesMDT-data group Number of reuse10.9.9.8 310.9.9.9 2Configuration Examples for Multicast VPN
This section contains the following configuration examples:
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Configuring MVPN and SSM: Example
In the following example, PIM-SSM is configured in the backbone. Therefore, the default and data MDT groups are configured within the SSM range of IP addresses. Inside the VPN, PIM-SM is configured and only Auto-RP announcements are accepted.
ip vrf vrf1rd 1:1route-target export 1:1route-target import 1:1mdt default 232.0.0.1mdt data 232.0.1.0 0.0.0.255 threshold 500 list 101!ip pim ssm defaultip pim vrf vrf1 accept-rp auto-rpEnabling a VPN for Multicast Routing: Example
In the following example, multicast routing is enabled with a VPN routing instance named vrf1:
ip multicast-routing vrf1Configuring the MDT Address Family in BGP for Multicast VPN: Example
In the following example, an MDT address family session is configured on a PE router to establish MDT peering sessions for MVPN.
!ip vrf testrd 55:2222route-target export 55:2222route-target import 55:2222mdt default 232.0.0.1!ip multicast-routingip multicast-routing vrf test!router bgp 55...!address-family vpnv4neighbor 192.168.1.1 activateneighbor 192.168.1.1 send-community both!address-family ipv4 mdtneighbor 192.168.1.1 activateneighbor 192.168.1.1 send-community both!Configuring the Multicast Group Address Range for Data MDT Groups: Example
In the following example, the VPN routing instance is assigned a VRF named blue. The MDT default group for a VPN VRF is 239.1.1.1, and the multicast group address range for MDT groups is 239.1.2.0 with wildcard bits of 0.0.0.3:
ip vrf bluerd 55:1111route-target both 55:1111mdt default 239.1.1.1mdt data 239.1.2.0 0.0.0.3endConfiguring the IP Source Address of Register Messages: Example
In the following example, the IP source address of the register message is configured to the Ethernet interface 1/0/1 of a DR:
ip pim register-source Ethernet1/0/1Configuring an MSDP Peer: Example
In the following example, an MSDP peer is configured with a VPN routing instance named vrf1 and a source of 10.10.0.1 from Ethernet interface 1/0/1:
ip msdp vrf vrf1 peer 10.10.0.1 connect-source Ethernet 1/0/1Limiting the Number of Multicast Routes: Example
In the following example, the number of multicast routes that can be added in to a multicast routing table is set to 200,000 and the threshold value of the number of mroutes that will cause a warning message to occur is set to 20,000:
!ip multicast-routing distributedip multicast-routing vrf cisco distributedip multicast cache-headersip multicast route-limit 200000 20000ip multicast vrf cisco route-limit 200000 20000no mpls traffic-eng auto-bw timers frequency 0!Additional References
The following sections provide references related to the configuring Multicast VPN.
Related Documents
Extranet MVPN concepts, tasks, and configuration examples
Inter-AS MVPN concepts, tasks, and configuration examples
MVPN MIB concepts and tasks
"Multicast VPN MIB" module
IP multicast commands: complete command syntax, command mode, command history, defaults, usage guidelines, and examples
Cisco IOS IP Multicast Command Reference, Release 12.4
Standards
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
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MIBs
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To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:
RFCs
No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.
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Technical Assistance
Feature Information for Configuring Multicast VPN
Table 2 lists the release history for this feature.
Table 2 lists the features in this module and provides links to specific configuration information. Only features that were introduced or modified in Cisco IOS Releases 12.2(1) or 12.0(3)S or a later release appear in the table.
For information on a feature in this technology that is not documented here, see the IP Multicast Features Roadmap.
Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.
© 2005-2010 Cisco Systems, Inc. All rights reserved.
