MVPN Configuration Guide

Configuring Multicast VPN

The 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

For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for Configuring Multicast VPN" section.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS XE 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

•Prerequisites for Configuring Multicast VPN

•Restrictions for Configuring Multicast VPN

•Information About Configuring Multicast VPN

•How to Configure Multicast VPN

•Configuration Examples for Multicast VPN

•Additional References

•Feature Information for Configuring Multicast VPN

Prerequisites for Configuring Multicast VPN

•Before performing the tasks in this module, you should be familiar with the concepts described in the "IP Multicast Technology Overview" module.

•The tasks in this module assume that IP multicasting has been enabled and that the Protocol Independent Multicast (PIM) interfaces have been configured using the tasks described in the"Configuring Basic IP Multicast" module.

Restrictions for Configuring Multicast VPN

•The update source interface for the Border Gateway Protocol (BGP) peerings must be the same for all BGP peerings configured on the router in order for the default multicast distribution tree (MDT) to be configured properly. If you use a loopback address for BGP peering, then PIM sparse mode must be enabled on the loopback address.

•The ip mroute-cache command must be enabled on the loopback interface used as the BGP peering interface in order for distributed multicast switching to function on the platforms that support it. The no ip mroute-cache command must not be present on these interfaces.

•MVPN does not support multiple BGP peering update sources.

•Data MDTs are not created for VPN routing and forwarding instance (VRF) PIM dense mode multicast streams because of the flood and prune nature of dense mode multicast flows and the resulting periodic bring-up and tear-down of such data MDTs.

•Multiple BGP update sources are not supported and configuring them can break MVPN reverse path forwarding (RPF) checking. The source IP address of the MVPN tunnels is determined by the highest IP address used for the BGP peering update source. If this IP address is not the IP address used as the BGP peering address with the remote provider edge (PE) router, MVPN will not function properly.

•When a customer configures an ASR 1000 series router as a PE router in an MVPN network, the PE router may be subject to multicast traffic duplication after an RP switchover. All MVPN traffic will recover to normal replication state after a short period.

Information About Configuring Multicast VPN

Before you configure MVPN, you should understand the following concepts:

•Multicast VPN Operation

•Multicast VPN Routing and Forwarding and Multicast Domains

•Multicast Distribution Trees

•Multicast Tunnel Interface

•Benefits of Multicast VPN

Multicast VPN Operation

MVPN IP allows a service provider to configure and support multicast traffic in an MPLS VPN environment. This feature supports routing and forwarding of multicast packets for each individual 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.

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 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. After a PE router sends the UDP message, it waits 3 more seconds before switching over; 13 seconds is the worst case switchover time and 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 and 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.

Benefits of Multicast VPN

•Provides a scalable method to dynamically send information to multiple locations.

•Provides high-speed information delivery.

•Provides connectivity through a shared infrastructure.

How to Configure Multicast VPN

This section contains the following procedures.

•Configuring a Default MDT Group for a VRF (required)

•Configuring the MDT Address Family in BGP for Multicast VPN (required)

•Configuring the Data Multicast Group (optional)

•Configuring Multicast Routes and Information (optional)

•Verifying Information for the MDT Default Group (optional)

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.

SUMMARY STEPS

1. enable

2. configure terminal

3. ip multicast-routing

4. ip multicast-routing vrf vrf-name

5. ip vrf vrf-name

6. mdt default group-address

DETAILED STEPS

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.

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 BGP MDT Subaddress Family Identifier (SAFI) updates.

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 XE 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.

Note Prior to the introduction of MDT SAFI support, the BGP extended community attribute was used as an interim solution to advertise the IP address of the source PE and default MDT group before IETF standardization. A BGP extended community attribute in an MVPN environment, however, has certain limitations: it cannot be used in inter-AS scenarios (because the attribute is nontransitive), and it uses RD Type 2 (which is not a supported standard).

BGP MDT SAFI

In Cisco IOS XE 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.

Note To prevent backwards-compatibility issues, BGP allows the communication of the older style updates with peers that are unable to understand the MDT SAFI address family.

In Cisco IOS XE 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.

Automigration to the MDT SAFI

When a Cisco IOS XE release is migrated 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.

Note Because there is no VRF configuration on route reflectors (RRs), automigration to the MDT SAFI will not be triggered on RRs. The MDT SAFI configuration, thus, will need to be manually configured on RRs. Having a uniform MDT transmission method will reduce processing time on the routers (because MDT SAFI conversion is not necessary).

Guidelines for Configuring the MDT SAFI

•We recommend that you configure the MDT SAFI on all routers that participate in the MVPN. Even though the benefits of the MDT SAFI are for SSM tree building, the MDT SAFI must also be configured when using MVPN with the default MDT group for PIM-SM. From the multicast point of view, the MDT SAFI is not required for MVPN to work within a PIM-SM core. However, in certain scenarios, the new address family must be configured in order to create the MTI. Without this notification, the MTI would not be created and MVPN would not function (even with PIM-SM).

•For backward-compatible sessions, extended communities must be enabled on all MDT SAFI peers. In a pure MDT SAFI environment there is no need to configure extended communities explicitly for MVPN. However, extended communities will be needed for VPNv4 interior BGP (iBGP) sessions to relay the route-target. In a hybrid (MDT SAFI and pre-MDT SAFI) environment, extended communities must be configured to send the embedded source in the VPNv4 address and the MDT group address to MDT SAFI neighbors.

Guidelines for Upgrading a Network to Support the MDT SAFI

When moving from a pre-MDT SAFI to an MDT SAFI environment, the utmost 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 recommend that you perform the following steps:

1. Upgrade the PEs in the MVPN to a Cisco IOS XE release that supports the MDT SAFI. Upon bootup, the PE configurations will be automigrated to the MDT SAFI. For more information about the automigration to the MDT SAFI functionality, see the "Automigration to the MDT SAFI" section.

2. After the PEs have been upgraded, upgrade the RRs and enable the MDT SAFI for all peers providing MVPN service. Enabling or disabling the MDT SAFI will reset the BGP peer relationship for all address families; thus, a loss of routing information may occur.

Note In the case of a multihomed BGP RR scenario, one of the RRs must be upgraded and configured last. The upgraded PEs will use this RR to relay MDT advertisements while the other RRs are being upgraded.

Supported Policy

The following policy configuration parameters are supported under the MDT SAFI:

•Mandatory attributes and well-known attributes, such as the AS-path, multiexit discriminator (MED), BGP local-pref, and next hop attributes.

•Standard communities, community lists, and route maps.

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:

•Route-originator attribute

•Network Layer Reachability Information (NLRI) prefix filtering (prefix lists, distribute lists)

•Extended community attributes (route target and site of origin)

SUMMARY STEPS

1. enable

2. configure terminal

3. router bgp as-number

4. address-family ipv4 mdt

5. neighbor neighbor-address activate

6. neighbor neighbor-address send-community [both | extended | standard]

7. exit

8. address-family vpnv4

9. neighbor neighbor-address activate

10. neighbor neighbor-address send-community [both | extended | standard]

11. end

DETAILED STEPS

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.

Prerequisites

•Before configuring a default MDT group, the VPN must be configured for multicast routing as described in the "Configuring a Default MDT Group for a VRF" section.

•All access lists needed when using the tasks in this module should be configured prior to beginning the configuration task. For information about how to configure an access list, see the "Creating an IP Access List and Applying It to an Interface" module.

SUMMARY STEPS

1. enable

2. configure terminal

3. ip vrf vrf-name

4. mdt data group-address-range wildcard-bits [threshold threshold-value] [list access-list]

5. mdt log-reuse

6. exit

DETAILED STEPS

Configuring Multicast Routes and Information

Perform this task to limit the number of multicast routes that can be added in a router.

Prerequisites

•Before configuring a default MDT group, the VPN must be configured for multicast routing as described in the "Configuring a Default MDT Group for a VRF" section.

•All access lists needed when using the tasks in this module should be configured prior to beginning the configuration task. For information about how to configure an access list, see the "Creating an IP Access List and Applying It to an Interface" module.

SUMMARY STEPS

1. enable

2. configure terminal

3. ip multicast vrf vrf-name route-limit limit [threshold]

4. ip multicast mrinfo-filter access-list

DETAILED STEPS

Verifying Information for the MDT Default Group

Perform this task to verify information about the MDT default group.

SUMMARY STEPS

1. enable

2. show ip msdp [vrf vrf-name] peer [peer-address | peer-name]

3. show ip msdp [vrf vrf-name] summary

4. show ip pim [vrf vrf-name] mdt bgp

5. show ip pim [vrf vrf-name] mdt send

6. show ip pim mdt history

DETAILED STEPS

Step 1 enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Router> enable

Step 2 show ip msdp [vrf vrf-name] peer [peer-address | peer-name]

Enter the show ip msdp peer command to verify detailed information about MSDP peer 224.135.250.116:

Router# show ip msdp peer 224.135.250.116 

MSDP 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: 436765/429062 

   Output messages discarded: 0 

   Connection and counters cleared 1w2d     ago 

 SA Filtering: 

   Input (S,G) filter: none, route-map: none 

   Input RP filter: none, route-map: none 

   Output (S,G) filter: none, route-map: none 

   Output RP filter: none, route-map: none 

 SA-Requests: 

   Input filter: none 

   Sending SA-Requests to peer: disabled 

 Peer ttl threshold: 0 

 SAs learned from this peer: 32, SAs limit: 500 

 Input queue size: 0, Output queue size: 0 

Step 3 show ip msdp [vrf vrf-name] summary

Enter the show ip msdp summary command to display MSDP peer status:

Router# show ip msdp summary 

MSDP Peer Status Summary 

Peer Address     AS    State    Uptime/  Reset SA    Peer Name 

                                Downtime Count Count 

224.135.250.116  109   Up       1d10h    9     111   rtp5-rp1 

*144.228.240.253 1239  Up       14:24:00 5     4010  sl-rp-stk 

172.16.253.19    109   Up       12:36:17 5     10    rtp4-rp1 

172.16.170.110   109   Up       1d11h    9     12    ams-rp1 

Step 4 show ip pim [vrf vrf-name] mdt bgp

To display information about and to verify information about the BGP advertisement of the RD for the MDT default group, use the show ip pim mdt bgp command in privileged EXEC mode:

Router# show ip pim mdt bgp 
 
MDT-default group 232.2.1.4 rid:1.1.1.1 next_hop:1.1.1.1 

Step 5 show ip pim [vrf vrf-name] mdt send

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 send 

MDT-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           1 

Step 6 show ip pim mdt history

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 20 

   MDT-data send history for VRF - vrf1 for the past 20 minutes 

MDT-data group        Number of reuse 

     10.9.9.8           3 

     10.9.9.9           2 

Configuration Examples for Multicast VPN

This section contains the following configuration examples:

•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

•Limiting the Number of Multicast Routes: Example

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 vrf1 

 rd 1:1 

 route-target export 1:1 

 route-target import 1:1 

 mdt default 232.0.0.1 

 mdt data 232.0.1.0 0.0.0.255 threshold 500 list 101 

! 

ip pim ssm default 

ip pim vrf vrf1 accept-rp auto-rp 

Enabling a VPN for Multicast Routing: Example

In the following example, multicast routing is enabled with a VPN routing instance named vrf1:

ip multicast-routing vrf1 

Configuring 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 test

 rd 55:2222

 route-target export 55:2222

 route-target import 55:2222

 mdt default 232.0.0.1

!

ip multicast-routing

ip multicast-routing vrf test

!

router bgp 55

.

.

.

!

 address-family vpnv4

 neighbor 192.168.1.1 activate

 neighbor 192.168.1.1 send-community both

!

 address-family ipv4 mdt

 neighbor 192.168.1.1 activate

 neighbor 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 blue 

 rd 55:1111 

 route-target both 55:1111 

 mdt default 239.1.1.1 

 mdt data 239.1.2.0 0.0.0.3 

 end 

Limiting 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 distributed 

ip multicast-routing vrf cisco distributed 

ip multicast cache-headers 

ip multicast route-limit 200000 20000 

ip multicast vrf cisco route-limit 200000 20000 

no mpls traffic-eng auto-bw timers frequency 0 

! 

Additional References

The following sections provide references related to the configuring Multicast VPN.

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for Configuring Multicast VPN

Table 2 lists the release history for this feature.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS XE 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 Table 2 lists only the Cisco IOS XE software release that introduced support for a given feature in a given Cisco IOS XE software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.

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