Configuring MVPNs

This chapter contains information on how to configure multicast virtual private networks (MVPNs)

About MVPNs

The multicast virtual private networks (MVPNs) feature allows you to support multicast connectivity over Layer 3 VPN. IP multicast is used to stream video, voice, and data to an VPN network core.

Historically, point-to-point tunnels were the only way to connect through an enterprise or service provider network. Although such tunneled networks had scalability issues, they were the only means of passing IP multicast traffic through a virtual private network (VPN). Because Layer 3 VPNs support only unicast traffic connectivity, deploying with a Layer 3 VPN allows operators to offer both unicast and multicast connectivity to Layer 3 VPN customers

MVPNs allows you to configure and support multicast traffic in an MVPN environment. MVPNs support routing and forwarding of multicast packets for each individual virtual routing and forwarding (VRF) instance, and it also provides a mechanism to transport VPN multicast packets across the enterprise or service provider backbone. IP multicast is used to stream video, voice, and data to a VPN network core.

A VPN allows 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.

MVPNs allow an enterprise to transparently interconnect its private network across the network backbone. Using MVPNs to interconnect an enterprise network does not change the way that an enterprise network is administered and it does not change general enterprise connectivity.

MVPN Routing and Forwarding and Multicast Domains

MVPNs introduce 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, the router forwards the data or control packets according to the information in the MVPN routing and forwarding (MVRF).

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 that are associated with that enterprise.

Multicast Distribution Trees

MVPNs establish a static default multicast distribution tree (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.

MVPNs also support the dynamic creation of MDTs for high-bandwidth transmission. Data MDTs are intended for high-bandwidth sources such as full-motion video inside the VPN to ensure optimal traffic forwarding in the VPN core.

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 that are 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. The following figure 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 that is 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 that is associated with the multicast session source, receives the request. The following figure depicts that the PE router forwards the request to the CE router that is 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. 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 joins the data MDT and receives traffic on it. (If the data MDT had not been configured and only the default MDT had been configured, all the customer sites would have received the traffic even though they were not interested in it.) PE routers maintain a PIM relationship with other PE routers over the default MDT and a PIM relationship with its directly attached P routers.

Multicast Tunnel Interface

An MVPN routing and forwarding (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 that the MVRF uses to access the multicast domain. The interface is a conduit that connects an MVRF and the global MVRF. One tunnel interface is created per MVRF.

Benefits of MVPNs

The benefits of MVPNs are as follows:

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

  • Provides high-speed information delivery.

  • Provides connectivity through a shared infrastructure.

BGP Advertisement Method - MVPN Support

When you configure the default MDT 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. 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 a rendezvous point (RP). The source provider edge (PE) address and default MDT address are sent using the Border Gateway Protocol (BGP).

BGP MDT SAFI

BGP MDT SAFI is the BGP advertisement method that is used for MVPNs. In the current release, only IPv4 is supported. MDT SAFI has the following settings:

  • AFI = 1

  • SAFI = 66

In Cisco NX-OS, the source PE address and the MDT address are passed to PIM using BGP MDT SAFI updates. The Route Descriptor (RD) type has changed to RD type 0 and BGP determines the best path for the MDT updates before passing the information to PIM.

You must configure the MDT SAFI address family for BGP neighbors by using the address-family ipv4 mdt command. You must still enable neighbors that do not support the MDT SAFI for the MDT SAFI in the local BGP configuration. Prior to the MDT SAFI, additional BGP configuration from the VPNv4 unicast configuration was not needed to support MVPNs.

Prerequisites for MVPNs

MVPNs configuration has the following prerequisites:

  • Ensure that you have configured MPLS and Label Distribution Protocol (LDP) in your network. All routers in the core, including the PE routers, must be able to support MPLS forwarding. VPNv4 routes are not installed by BGP if labeled paths do not exist for PE source addresses.

  • Ensure that you have installed the correct license for MPLS and any other features you will be using with MPLS.

Guidelines and Limitations for MVPNs

Configuring MVPNs has the following guidelines and limitations:

  • MVPNs are supported beginning with Cisco NX-OS Release 9.3(3).

  • MVPNs are supported only for Cisco Nexus 9500 platform switches with -R/-RX line cards (except the N9K-X96136YC-R line card).

  • Bidirectional Forwarding Detection (BFD) is not supported on the Multicast Tunnel Interface (MTI).

  • By default, the BGP update source is used as the source of the MVPN tunnel. However, you can use the mdt source to override the BGP update source and provide a different source to the multicast tunnel.

  • MVPN supports a maximum of 16 MDT source interfaces.

  • You must configure the MDT SAFI on all routers that participate in the MVPN operations.

  • Extended communities are needed for VPNv4 interior BGP (iBGP) sessions to carry the connector attribute.

  • MDT MTU configuration is not supported. The maximum customer multicast packet size that can be sent over MVPN is limited by the MTU of the core interfaces. For example:

    • MTU 1500 – Customer IP packet size = 1476

    • MTU 9216 – Customer IP packet size = 9192

  • Some of the MVPN multicast control packets are classified into the copp-system-p-class-l2-default CoPP policy. We recommend modifying the CoPP policy to increase the policer rate under this class if the violated count increases.

  • MDT bidir-enable is not supported.

  • vPCs are not supported for MVPN.

  • Data MDT entries are not cached when the transit PE router does not have receivers and is connected to a CE which is a RP. The data MDT entries are cached only when a local receiver is attached to this PE router. However, there is a delay in the switchover because the entries are not pre-downloaded.

  • For Date MDT, only 'immediate-switch' mode is supported. Threshold based switching is not supported.

  • Sub-interface and SVI support between PE and P /PE devices is not available.

  • MVPN Consistency-checker is not supported in Cisco Nexus Release 9.3(3).

  • Statistics for MTI interfaces are not supported in Cisco Nexus Release 9.3(3).

  • Maximum 40G multicast traffic per ASIC is supported in Cisco Nexus Release 9.3(3).

  • You are allowed to configure a non-default MTU on a VRF only after you remove the MDT MTU configuration from the VRF. This occurs when the MTI is down in a switch in which the VRF with the non-default MDT MTU is available.

  • Due to a hardware limitation, the MTI TX packet counts are not supported. However, all MTI RX packet and byte counts are supported.

Default Settings for MVPNs

Table 1. Default MVPN Parameters

Parameters

Default

mdt default address

No default

mdt enforce-bgp-mdt-safi

Enabled

mdt source

No default

mdt ip pim hello-interval interval

30000 ms

mdt ip pim jp-interval interval

60000 ms

mdt default asm-use-shared-tree

Disabled

Configuring MVPNs

This chapter describes how to configure multicast virtual private networks (MVPNs) on Cisco NX-OS devices.


Note
For MVPN, a new TCAM region "ing-mvpn" is used (with default size of 10). This region is carved automatically hence you need not carve it. To verify if this TCAM region is carved or not, you can use the following commands:
switch# show hardware access-list tcam region | i ing-mvpn
Ingress mVPN [ing-mvpn] size = 10
switch#

If the region is not carved due to any reason (size shows is 0), you can use the following command to carve the TCAM region to size 10 and reload the device. The TCAM is expected to be carved to size 10. 

switch (config)# hardware access-list tcam region ing-mvpn 10
WARNING: On module 2,
WARNING: On module 4,
Warning: Please reload all linecards for the configuration to take effect
switch (config)#

Enabling MVPNs

Beginning with Cisco NX-OS Release 9.3(3), you can configure MVPNs on Cisco Nexus 9500-R switches.

Before you begin

You must install and enable the MPLS feature set using the install feature-set mpls and feature-set mpls commands.

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch#configure terminal
switch(config)#

Enters global configuration mode.

Step 2

feature bgp

Example:

switch(config)#feature bgp

Enables BGP feature and configurations.

Step 3

feature pim

Example:

switch(config)#feature pim

Enables the PIM feature.

Step 4

feature mvpn

Example:

switch(config)#feature mvpn

Enables the MVPN feature.

Step 5

feature mpls l3vpn

Example:

switch(config)#feature mpls l3vpn

Enables the MPLS Layer 3 VPN feature. This determines the unicast routes across sites.

Step 6

feature mpls ldp

Example:

switch(config)#feature mpls ldp

Enables the MPLS Label Distribution Protocol (LDP).

Enabling PIM on Interfaces

You can configure Protocol Independent Multicast (PIM) on all interfaces that are used for IP multicast. We recommend that you configure PIM sparse mode on all physical interfaces of provider edge (PE) routers that connect to the backbone. We also recommend that you configure PIM sparse mode on all loopback interfaces if they are used for BGP peering or if their IP address is used as an RP address for PIM.

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch#configure terminal
switch(config)#

Enters global configuration mode.

Step 2

ip pim sparse-mode

Example:

switch(config)#ip pim sparse-mode

Enables PIM sparse mode on the interface.

Configuring a Default MDT for a VRF

You can configure a default MDT for a VRF.

Before you begin

The default MDT must be the same that is configured on all routers that belong to the same VPN. The source IP address is the address that you use to source the BGP sessions.

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch#configure terminal
switch(config)#

Enters global configuration mode.

Step 2

vrf context VRF_NAME

Example:

switch(config)#vrf context vrf1

Configures the VRF.

Step 3

mdt default address

Example:

switch(config)#mdt default 232.0.0.1

Configures the multicast address range for data MDTs for a VRF as follows:

  • A tunnel interface is created as a result of this command.

  • By default, the destination address of the tunnel header is the address argument.

Configuring MDT SAFI for a VRF

By default, MDT subsequent address family identifiers (SAFI) for a VRF are enforced. If desired, you can configure MDT to interoperate with peers that do not support MDT SAFI.

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch#configure terminal
switch(config)#

Enters global configuration mode.

Step 2

vrf context VRF_NAME

Example:

switch(config)#vrf context vrf1
switch(config-vrf)#

Configures the VRF.

Step 3

no mdt enforce-bgp-mdt-safi

Example:

switch(config-vrf)#no mdt enforce-bgp-mdt-safi

Enables MDT to interoperate with peers that do not support MDT SAFI. Initially only the (*,G) entry for the default MDT group is populated if it falls within the Any Source Multicast (ASM) range. Then later, based on traffic, the (S,G) entries are learned like regular ASM routes.

Removing the no option from the command enforces the use of MDT SAFI for the specified VRF.

Configuring the MDT Address Family in BGP for MVPNs

You can configure an MDT address family session on PE routers to establish MDT peering sessions for MVPNs.

Use the address-family ipv4 mdt command under neighbor mode to configure an MDT address-family session. MDT address-family sessions are used to pass the source PE address and MDT address to PIM using BGP MDT Subaddress Family Identifier (SAFI) updates.

Before you begin

Before MVPN peering can be established through an MDT address family, you must configure MPLS in the BGP network and multiprotocol BGP on PE routers that provide VPN services to CE routers.

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch#configure terminal
switch(config)#

Enters global configuration mode.

Step 2

feature bgp as-number

Example:

switch(config)#feature bgp 65635

Enters switch configuration mode and creates a BGP routing process.

Step 3

vrf context VRF_NAME

Example:

switch(config)#vrf context vpn1
switch(config-vrf)#

Defines a VPN routing instance identified by vrf-name and enters VRF configuration mode. The vrf-name argument is any case-sensitive, alphanumeric string up to 32 characters.

Step 4

rd route-distinguisher

Example:

switch(config-vrf)#rd 1.2.1

Assigns a route distinguisher to the VRF vrf-name. The route-distinguisher argument adds an 8-byte value to an IPv4 prefix to create a VPN IPv4 prefix. You can enter an RD in either of these formats:

  • 16-bit or 32-bit AS number: your 32-bit number, for example, 1.2:3

  • 32-bit IP address: your 16-bit number, for example, 192.0.2.1:1

Step 5

address-family ipv4 unicast

Example:

switch(config-vrf)#address-family ipv4unicast
switch(config-vrf-af)#

Specifies the IPv4 address family type and enters address family configuration mode

Step 6

route-target import route-target-ext-community

Example:

switch(config-vrf-af)# route-target import 1.0.1

Specifies a route-target extended community for a VRF. The import keyword imports routing information from the target VPN extended community.

The route-target-ext-community argument adds the route-target extended community attributes to the VRF list of import route-target extended communities. You can enter the route-target-ext-community argument in either of these formats:

  • 16-bit or 32-bit AS number: your 32-bit number, for example, 1.2:3

  • 32-bit IP address: your 16-bit number, for example, for example, 192.0.2.1:1

Step 7

route-target export route-target-ext-community

Example:

switch(config-vrf-af)# route-target export 1.0.1

Specifies a route-target extended community for a VRF. The export keyword imports routing information from the target VPN extended community.

The route-target-ext-community argument adds the route-target extended community attributes to the VRF list of import route-target extended communities. You can enter the route-target-ext-community argument in either of these formats:

  • 16-bit or 32-bit AS number: your 32-bit number, for example, 1.2:3

  • 32-bit IP address: your 16-bit number, for example, for example, 192.0.2.1:1

Step 8

router bgp as-number

Example:

switch(config)#router bgp 1.1
switch(config-router)#

Configures a BGP routing process and enters router configuration mode. The as-number argument indicates the number of an autonomous system that identifies the router to other BGP routers and tags the routing information passed along. The AS number can be a 16-bit integer or a 32-bit integer in the form of a higher 16-bit decimal number and a lower 16-bit decimal number in xx.xx format.

Step 9

address-family ipv4 mdt

Example:

switch(config-router)#address-family ipv4 mdt

Enters IPv4 MDT address family configuration mode.

Step 10

address-family {vpn4} [unicast]

Example:

switch(config-router-af)# address-family vpnv4
switch(config-router-af)#

Enters address family configuration mode for configuring routing sessions, such as BGP, that use standard VPNv4 or VPNv6 address prefixes. The optional unicast keyword specifies VPNv4 or VPNv6 unicast address prefixes.

Step 11

address-family {ipv4} unicast

Example:

switch(config-router-af)# address-family ipv4 unicast
switch(config-router-af)#

Enters address family configuration mode for configuring routing sessions that use standard IPv4 or IPv6 address prefixes.

Step 12

neighbor neighbor-address

Example:

switch(config-switch-af)# neighbor 192.168.1.1

Enters neighbor configuration mode.

Step 13

update source interface

Example:

switch(config-switch-neighbor)# update-source loopback 1

Sets the update source as loopback1.

Step 14

address-family ipv4 mdt

Example:

switch(config-router-neighbor)# address-family ipv4 mdt

Enters address family configuration mode to create an IP MDT address family session.

Step 15

send-community extended

Example:

switch(config-router-neighbor-af)#send-community extended

Specifies that extended communities attribute should be sent to a BGP neighbor.

Step 16

show bgp {ipv4} unicast neighbors vrfVRF_NAME

Example:

switch(config-router-neighbor-af)#show bgp ipv4 unicast neighbors vrf vpn1

Displays information about BGP neighbors. The vrf-name argument is any case-sensitive, alphanumeric string up to 32 characters.

Step 17

copy running-config startup-config

Example:

switch(config-router-neighbor-af)#copy running-config startup-config

Copies the running configuration to the startup configuration.

Configuring a Data MDT

You can configure a data MDT. Multicast groups that are used to create the data MDT are dynamically chosen from a pool of configured IP addresses. If the number of streams is greater than the maximum number of data MDTs per VRF per PE, multiple streams share the same data MDT.

Before you begin

Before configuring a data MDT, you must configure the default MDT on the VRF.

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

switch#configure terminal
switch(config)#

Enters global configuration mode.

Step 2

vrf context VRF_NAME

Example:

switch#ip vrf vrf1

Enters VRF configuration mode and defines the VPN routing instance by assigning a VRF name.

Step 3

mdt data prefix [immediate-switch] [route-map policy-name]

Example:

switch(config-vrf)# mdt data 225.1.1.1/32 immediate-switch route-map test

Example:

switch(config-vrf)# mdt data 225.1.1.1/32 route-map test

Specifies a range of values as follows:

  • The prefix specifies the range of addresses to be used in the data MDT pool.

  • The policy-name defines a policy file that defines which customer data streams should be considered for switching onto the data MDT.

Note

 

Entering this command with or without the immediate-switch option has the same effect.

Step 4

exit

Example:

switch(config)#exit

Returns to global configuration mode.

Verifying the MVPN Configuration

To display the MVPN configuration, perform one of the following tasks:

Table 2. Verifying the MVPN Configuration

Command

Purpose

show interface

Displays details of an interface.

show ip mroute vrf

Displays multicast routes.

show ip pim event-history mvpn

Displays the details of the MVPN event history logs.

show ip pim mdt

Displays the details of MTI tunnels created by MVPN.

show ip pim mdt receive vrf vrf-name

Displays the mapping of the customer source, the customer group to data MDT source, and the data MDT group on the receiving side.

show ip pim mdt send vrf vrf-name

Displays the mapping of the customer source, the customer group to data MDT source, and the data MDT group on the sending side.

show ip pim neighbor

Displays details of established PIM neighbors.

show ip route detail

Displays the details of the unicast routing tables.

show mvpn bgp mdt-safi

Displays the BGP MDT SAFI database in MVPN.

show mvpn mdt encap vrf vrf

Displays the encapsulation table in MVPN. This table indicates how MVPN packets are encapsulated when sent out on the default vrf.

show mvpn mdt route

Displays details of the default and MDT routes. This data determines how customer data and control traffic is sent on the default VRF.

show routing [ip] multicast mdt encap

Displays the encapsulation table in the MRIB. This table indicates how MVPN packets are encapsulated when sent out on the default vrf.

Configuration Examples for MVPN

The following example shows how to configure an MVPN with two contexts: 


vrf context vpn1
  ip pim rp-address 10.10.1.2 -list 224.0.0.0/8
  ip pim ssm range 232.0.0.0/8
  rd auto
  mdt default 232.1.1.1
  mdt source loopback1
  mdt data 225.122.111.0/24 immediate-switch
vrf context vpn4
  ip pim rp-address 10.10.4.2 -list 224.0.0.0/8
  ip pim ssm range 232.0.0.0/8
  mdt default 235.1.1.1
  mdt asm-use-shared-tree
ip pim rp-address 10.11.0.2 -list 224.0.0.0/8
ip pim rp-address 10.11.0.4 -list 235.0.0.0/8
ip pim ssm range 232.0.0.0/8
The following example shows how to assign to the VPN routing instance a VRF named blue. The MDT default for a VPN VRF is 10.1.1.1, and the multicast address range for MDTs is 10.1.2.0 with wildcard bits of 0.0.0.3:

Vrf context blue
mdt data 225.122.111.0/24 immediate-switch