Configuring MSDP

This chapter describes how to configure Multicast Source Discovery Protocol (MSDP) on a Cisco NX-OS device.

This chapter includes the following sections:

Information About MSDP

You can use the Multicast Source Discovery Protocol (MSDP) to exchange multicast source information between multiple BGP-enabled Protocol Independent Multicast (PIM) sparse-mode domains. For information about PIM, see Chapter1, “Configuring PIM and PIM6” For information about BGP, see the Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 5.x .

When a receiver for a group matches the group transmitted by a source in another domain, the rendezvous point (RP) sends PIM join messages in the direction of the source to build a shortest path tree. The designated router (DR) sends packets on the source-tree within the source domain, which may travel through the RP in the source domain and along the branches of the source-tree to other domains. In domains where there are receivers, RPs in those domains can be on the source-tree. The peering relationship is conducted over a TCP connection.

Figure 1-1 shows four PIM domains. The connected RPs (routers) are called MSDP peers because each RP maintains its own set of multicast sources. Source host 2 sends the multicast data to group 224.1.1.1. On RP 6, the MSDP process learns about the source through PIM register messages and generates Source-Active (SA) messages to its MSDP peers that contain information about the sources in its domain. When RP 3 and RP 5 receive the SA messages, they forward them to their MSDP peers. When RP 5 receives the request from host 2 for the multicast data on group 224.1.1.1, it builds a shortest path tree to the source by sending a PIM join message in the direction of host 1 at 192.1.1.1.

Figure 1-1 MSDP Peering Between RPs in Different PIM Domains

 

When you configure MSDP peering between each RP, you create a full mesh. Full MSDP meshing is typically done within an autonomous system, as shown between RPs 1, 2, and 3, but not across autonomous systems. You use BGP to do loop suppression and MSDP peer-RPF to suppress looping SA messages. For more information about mesh groups, see the “MSDP Mesh Groups” section.

Note You do not need to configure MSDP in order to use Anycast-RP (a set of RPs that can perform load balancing and failover) within a PIM domain. For more information, see the “Configuring a PIM Anycast-RP Set” section.

For detailed information about MSDP, see RFC 3618 .

This section includes the following topics:

SA Messages and Caching

MSDP peers exchange Source-Active (SA) messages that the MSDP software uses to propagate information about active sources. SA messages contain the following information:

  • Source address of the data source
  • Group address that the data source uses
  • IP address of the RP or the configured originator ID

When a PIM register message advertises a new source, the MSDP process reencapsulates the message in an SA message that is immediately forwarded to all MSDP peers.

The SA cache holds the information for all sources learned through SA messages. Caching reduces the join latency for new receivers of a group because the information for all known groups can be found in the cache. You can limit the number of cached source entries by configuring the SA limit peer parameter. You can limit the number of cached source entries for a specific group prefix by configuring the group limit global parameter.

The MSDP software sends SA messages for each group in the SA cache every 60 seconds or at the configured SA interval global parameter. An entry in the SA cache is removed if an SA message for that source and group is not received within SA interval plus 3 seconds.

MSDP Peer-RPF Forwarding

MSDP peers forward the SA messages that they receive away from the originating RP. This action is called peer-RPF flooding. The router examines the BGP or MBGP routing table to determine which peer is the next hop in the direction of the originating RP of the SA message. This peer is called a reverse path forwarding (RPF) peer.

If the MSDP peer receives the same SA message from a non-RPF peer in the direction of the originating RP, it drops the message. Otherwise, it forwards the message to all its MSDP peers.

MSDP Mesh Groups

You can use MSDP mesh groups to reduce the number of SA messages that are generated by peer-RPF flooding. In Figure 1-1, RPs 1, 2, and 3 receive SA messages from RP 6. By configuring a peering relationship between all the routers in a mesh and then configuring a mesh group of these routers, the SA messages that originate at a peer are sent by that peer to all other peers. SA messages received by peers in the mesh are not forwarded. An SA message that originates at RP 3 is forwarded to RP 1 and RP 2, but these RPs do not forward those messages to other RPs in the mesh.

A router can participate in multiple mesh groups. By default, no mesh groups are configured.

Virtualization Support

A virtual device context (VDC) is a logical representation of a set of system resources. Within each VDC, you can define multiple virtual routing and forwarding (VRF) instances. The MSDP configuration applies to the VRF selected within the current VDC.

You can use the 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 VDCs, see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 4.2.

For information about configuring VRFs, see the Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 5.x .

Licensing Requirements for MSDP

The following table shows the licensing requirements for this feature:

 

Product
License Requirement

Cisco NX-OS

MSDP requires an Enterprise Services license. For a complete explanation of the Cisco NX-OS licensing scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide .

Prerequisites for MSDP

MSDP has the following prerequisites:

  • You are logged onto the device.
  • You are in the correct virtual device context (VDC). A VDC is a logical representation of a set of system resources. You can use the switchto vdc command with a VDC number.
  • For global commands, you are in the correct virtual routing and forwarding (VRF) mode. The default configuration mode shown in the examples in this chapter applies to the default VRF.
  • You configured PIM for the networks where you want to configure MSDP.

Default Settings

Table 1-1 lists the default settings for MSDP parameters.

 

Table 1-1 Default MSDP Parameters

Parameters
Default

Description

Peer has no description

Administrative shutdown

Peer is enabled when it is defined

MD5 password

No MD5 password is enabled

SA policy IN

All SA messages are received

SA policy OUT

All registered sources are sent in SA messages

SA limit

No limit is defined

Originator interface name

RP address of the local system

Group limit

No group limit is defined

SA interval

60 seconds

Configuring MSDP

You can establish MSDP peering by configuring the MSDP peers within each PIM domain.

To configure MSDP peering, follow these steps:

Step 1 Select the routers to act as MSDP peers.

Step 2 Enable the MSDP feature. See the “Enabling the MSDP Feature” section.

Step 3 Configure the MSDP peers for each router identified in Step 1. See the “Configuring MSDP Peers” section.

Step 4 Configure the optional MSDP peer parameters for each MSDP peer. See the “Configuring MSDP Peer Parameters” section.

Step 5 Configure the optional global parameters for each MSDP peer. See the “Configuring MSDP Global Parameters” section.

Step 6 Configure the optional mesh groups for each MSDP peer. See the “Configuring MSDP Mesh Groups” section.

 

Note The MSDP commands that you enter before you enable MSDP are cached and then run when MSDP is enabled. Use the ip msdp peer or ip msdp originator-id command to enable MSDP.

This section includes the following topics:

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.

Enabling the MSDP Feature

Before you can access the MSDP commands, you must enable the MSDP feature.

SUMMARY STEPS

1. config t

2. feature msdp

3. (Optional) show running-configuration | grep feature

4. (Optional) copy running-config startup-config

DETAILED STEPS

 

 
Command
Purpose

Step 1

config t

 

Example:

switch# config t

switch(config)#

Enters configuration mode.

Step 2

feature msdp

 

Example:

switch# feature msdp

Enables the MSDP feature so that you can enter MSDP commands. By default, the MSDP feature is disabled.

Step 3

show running-configuration | grep feature

 

Example:

switch# show running-configuration | grep feature

(Optional) Shows feature commands that you specified.

Step 4

copy running-config startup-config

 

Example:

switch(config)# copy running-config startup-config

(Optional) Saves configuration changes.

Configuring MSDP Peers

You can configure an MSDP peer when you configure a peering relationship with each MSDP peer that resides either within the current PIM domain or in another PIM domain. MSDP is enabled on the router when you configure the first MSDP peering relationship.

BEFORE YOU BEGIN

Ensure that you have installed the Enterprise Services license and enabled PIM and MSDP.

Ensure that you configured BGP and PIM in the domains of the routers that you will configure as MSDP peers.

SUMMARY STEPS

1. config t

2. ip msdp peer peer-ip-address connect-source interface [ remote-as as-number ]

3. Repeat Step 2 for each MSDP peering relationship.

4. (Optional) show ip msdp summary [ vrf vrf-name | known-vrf-name | all ]

5. (Optional) copy running-config startup-config

DETAILED STEPS

 

 
Command
Purpose

Step 1

config t

 

Example:

switch# config t

switch(config)#

Enters configuration mode.

Step 2

ip msdp peer peer-ip-address connect-source interface [ remote-as as-number ]

 

Example:

switch(config)# ip msdp peer 192.168.1.10 connect-source ethernet 2/1 remote-as 8

Configures an MSDP peer with the specified peer IP address. The software uses the source IP address of the interface for the TCP connection with the peer. The interface can take the form of type slot/port . If the AS number is the same as the local AS, then the peer is within the PIM domain; otherwise, this peer is external to the PIM domain. By default, MSDP peering is disabled.

Note MSDP peering is enabled when you use this command.

Step 3

Repeat Step 2 for each MSDP peering relationship by changing the peer IP address, the interface, and the AS number as appropriate.

—

Step 4

show ip msdp summary [ vrf vrf-name | known-vrf-name | all ]

 

Example:

switch# show ip msdp summary

(Optional) Displays a summary of MDSP peers.

Step 5

copy running-config startup-config

 

Example:

switch(config)# copy running-config startup-config

(Optional) Saves configuration changes.

Configuring MSDP Peer Parameters

You can configure the optional MSDP peer parameters described in Table 1-2 . You configure these parameters in global configuration mode for each peer based on its IP address.

 

Table 1-2 MSDP Peer Parameters

Parameter
Description

Description

Description string for the peer. By default, the peer has no description.

Administrative shutdown

Method to shut down the MSDP peer. The configuration settings are not affected by this command. You can use this parameter to allow configuration of multiple parameters to occur before making the peer active. The TCP connection with other peers is terminated by the shutdown. By default, a peer is enabled when it is defined.

MD5 password

MD5-shared password key used for authenticating the peer. By default, no MD5 password is enabled.

SA policy IN

Route-map policy1 for incoming SA messages. By default, all SA messages are received.

SA policy OUT

Route-map policy 1 for outgoing SA messages. By default, all registered sources are sent in SA messages.

SA limit

Number of (S, G) entries accepted from the peer and stored in the SA cache. By default, there is no limit.

1.To configure route-map policies, see the Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 5.x.

For information about configuring multicast route maps, see the “Configuring Route Maps to Control RP Information Distribution” section.

Note For information about configuring mesh groups, see the “Configuring MSDP Mesh Groups” section.

BEFORE YOU BEGIN

Ensure that you have installed the Enterprise Services license and enabled PIM and MSDP.

SUMMARY STEPS

1. config t

2. ip msdp description peer-ip-address string

ip msdp shutdown peer-ip-address

ip msdp password peer-ip-address password

ip msdp sa-policy peer-ip-address policy-name in

ip msdp sa-policy peer-ip-address policy-name out

ip msdp sa-limit peer-ip-address limit

3. (Optional) show ip msdp peer [ peer-address ] [ vrf vrf-name | known-vrf-name | all ]

4. (Optional) copy running-config startup-config

DETAILED STEPS

 

 
Command
Purpose

Step 1

config t

 

Example:

switch# config t

switch(config)#

Enters configuration mode.

Step 2

ip msdp description peer-ip-address string

 

Example:

switch(config)# ip msdp description 192.168.1.10 peer in Engineering network

Sets a description string for the peer. By default, the peer has no description.

ip msdp shutdown peer-ip-address

 

Example:

switch(config)# ip msdp shutdown 192.168.1.10

Shuts down the peer. By default, the peer is enabled when it is defined.

ip msdp password peer-ip-address password

 

Example:

switch(config)# ip msdp password 192.168.1.10 my_md5_password

Enables an MD5 password for the peer. By default, no MD5 password is enabled.

ip msdp sa-policy peer-ip-address policy-name in

 

Example:

switch(config)# ip msdp sa-policy 192.168.1.10 my_incoming_sa_policy in

Enables a route-map policy for incoming SA messages. By default, all SA messages are received.

ip msdp sa-policy peer-ip-address policy-name out

 

Example:

switch(config)# ip msdp sa-policy 192.168.1.10 my_outgoing_sa_policy out

Enables a route-map policy for outgoing SA messages. By default, all registered sources are sent in SA messages.

ip msdp sa-limit peer-ip-address limit

 

Example:

switch(config)# ip msdp sa-limit 192.168.1.10 5000

Sets a limit on the number of (S, G) entries accepted from the peer. By default, there is no limit.

Step 3

show ip msdp peer [ peer-address ] [ vrf vrf-name | known-vrf-name | all ]

 

Example:

switch# show ip msdp peer 1.1.1.1

(Optional) Displays detailed MDSP peer information.

Step 4

copy running-config startup-config

 

Example:

switch(config)# copy running-config startup-config

(Optional) Saves configuration changes.

Configuring MSDP Global Parameters

You can configure the optional MSDP global parameters described in Table 1-3 .

 

Table 1-3 MSDP Global Parameters

Parameter
Description

Originator interface name

IP address used in the RP field of an SA message entry. When Anycast RPs are used, all RPs use the same IP address. You can use this parameter to define a unique IP address for the RP of each MSDP peer. By default, the software uses the RP address of the local system.

Note We recommend that you use a loopback interface for the RP address.

Group limit

Maximum number of (S, G) entries that the software creates for the specified prefix. The software ignores groups when the group limit is exceeded and logs a violation. By default, no group limit is defined.

SA interval

Interval at which the software transmits Source-Active (SA) messages. The range is from 60 to 65,535 seconds. The default is 60 seconds.

BEFORE YOU BEGIN

Ensure that you have installed the Enterprise Services license and enabled PIM and MSDP.

SUMMARY STEPS

1. config t

2. ip msdp originator-id interface

ip msdp group-limit limit source source-prefix

ip msdp sa-interval seconds

3. (Optional) show ip msdp summary [ vrf vrf-name | known-vrf-name | all ]

4. (Optional) copy running-config startup-config

DETAILED STEPS

 

 
Command
Purpose

Step 1

config t

 

Example:

switch# config t

switch(config)#

Enters configuration mode.

Step 2

ip msdp originator-id interface

 

Example:

switch(config)# ip msdp originator-id loopback0

Sets the IP address used in the RP field of an SA message entry. The interface can take the form of type slot/port . By default, the software uses the RP address of the local system.

Note We recommend that you use a loopback interface for the RP address.

ip msdp group-limit limit source source-prefix

 

Example:

switch(config)# ip msdp group-limit 1000 source 192.168.1.0/24

Maximum number of (S, G) entries that the software creates for the specified prefix. The software ignores groups when the group limit is exceeded and logs a violation. By default, no group limit is defined.

ip msdp sa-interval seconds

 

Example:

switch(config)# ip msdp sa-interval 80

Interval at which the software transmits Source-Active (SA) messages. The range is from 60 to 65,535 seconds. The default is 60 seconds.

Step 3

show ip msdp summary [ vrf vrf-name | known-vrf-name | all ]

 

Example:

switch# show ip msdp summary

(Optional) Displays a summary of the MDSP configuration.

Step 4

copy running-config startup-config

 

Example:

switch(config)# copy running-config startup-config

(Optional) Saves configuration changes.

Configuring MSDP Mesh Groups

You can configure optional MDSP mesh groups in global configuration mode by specifying each peer in the mesh. You can configure multiple mesh groups on the same router and multiple peers per mesh group.

BEFORE YOU BEGIN

Ensure that you have installed the Enterprise Services license and enabled PIM and MSDP.

SUMMARY STEPS

1. config t

2. ip msdp mesh-group peer-ip-addr mesh-name

3. Repeat Step 2 for each MSDP peer in the mesh.

4. show ip msdp mesh-group [ mesh-group ] [ vrf vrf-name | known-vrf-name | all ]

5. copy running-config startup-config

DETAILED STEPS

 

 
Command
Purpose

Step 1

config t

 

Example:

switch# config t

switch(config)#

Enters configuration mode.

Step 2

ip msdp mesh-group peer-ip-addr mesh-name

 

Example:

switch(config)# ip msdp mesh-group 192.168.1.10 my_mesh_1

Configures an MSDP mesh with the peer IP address specified. You can configure multiple meshes on the same router and multiple peers per mesh group. By default, no mesh groups are configured.

Step 3

Repeat Step 2 for each MSDP peer in the mesh by changing the peer IP address.

—

Step 4

show ip msdp mesh-group [ mesh-group ] [ vrf vrf-name | known-vrf-name | all ]

 

Example:

switch# show ip msdp summary

(Optional) Displays information about the MDSP mesh group configuration.

Step 5

copy running-config startup-config

 

Example:

switch(config)# copy running-config startup-config

(Optional) Saves configuration changes.

Restarting the MSDP Process

You can restart the MSDP process and optionally flush all routes.

BEFORE YOU BEGIN

Ensure that you have installed the Enterprise Services license and enabled PIM and MSDP.

SUMMARY STEPS

1. restart msdp

2. config t

3. ip msdp flush-routes

4. (Optional) show running-configuration | include flush-routes

5. (Optional) copy running-config startup-config

DETAILED STEPS

 

 
Command
Purpose

Step 1

restart msdp

 

Example:

switch# restart msdp

Restarts the MSDP process.

Step 2

config t

 

Example:

switch# config t

switch(config)#

Enters configuration mode.

Step 3

ip msdp flush-routes

 

Example:

switch(config)# ip msdp flush-routes

Removes routes when the MSDP process is restarted. By default, routes are not flushed.

Step 4

show running-configuration | include flush-routes

 

Example:

switch(config)# show running-configuration | include flush-routes

(Optional) Shows flush-routes configuration lines in the running configuration.

Step 5

copy running-config startup-config

 

Example:

switch(config)# copy running-config startup-config

(Optional) Saves configuration changes.

Verifying the MSDP Configuration

To display the MSDP configuration information, perform one of the following tasks:

 

Command
Purpose

show ip msdp count [ as-number ] [ vrf vrf-name | known-vrf-name | all ]

Displays MSDP (S, G) entry and group counts by the AS number.

show ip msdp mesh-group [ mesh-group ] [ vrf vrf-name | known-vrf-name | all ]

Displays the MSDP mesh group configuration.

show ip msdp peer [ peer-address ] [ vrf vrf-name | known-vrf-name | all ]

Displays MSDP information for the MSDP peer.

show ip msdp rpf [ rp-address ] [ vrf vrf-name | known-vrf-name | all ]

Displays next-hop AS on the BGP path to an RP address.

show ip msdp sources [ vrf vrf-name | known-vrf-name | all ]

Displays the MSDP-learned sources and violations of configured group limits.

show ip msdp summary [ vrf vrf-name | known-vrf-name | all ]

Displays a summary of the MSDP peer configuration.

For detailed information about the fields in the output from these commands, see the Cisco Nexus 7000 Series NX-OS Multicast Routing Command Reference, Release 5.x .

Monitoring MSDP

You can display and clear MSDP statistics by using the features in this section.

This section has the following topics:

Displaying Statistics

You can display MSDP statistics using the commands listed in Table 1-4 .

 

Table 1-4 MSDP Statistics Commands
Command
Purpose

show ip msdp [ as-number ] internal event-history { errors | messages }

Displays memory allocation statistics.

show ip msdp policy statistics sa-policy peer-address { in | out } [ vrf vrf-name | known-vrf-name | all ]

Displays the MSDP policy statistics for the MSDP peer.

show ip msdp { sa-cache | route } [ source-address ] [ group-address ] [ vrf vrf-name | known-vrf-name | all ] [ asn-number ] [ peer peer-address ]

Displays the MSDP SA route cache. If you specify the source address, all groups for that source are displayed. If you specify a group address, all sources for that group are displayed.

Clearing Statistics

You can clear the MSDP statistics using the commands listed in Table 1-5 .

 

Table 1-5 MSDP Clear Statistics Commands
Command
Description

clear ip msdp peer [ peer-address ] [ vrf vrf-name | known-vrf-name ]

Clears the TCP connection to an MSDP peer.

clear ip msdp policy statistics sa-policy peer-address { in | out } [ vrf vrf-name | known-vrf-name ]

Clears statistics counters for MSDP peer SA policies.

clear ip msdp statistics [ peer-address ] [ vrf vrf-name | known-vrf-name ]

Clears statistics for MSDP peers.

clear ip msdp { sa-cache | route } [ group-address ] [ vrf vrf-name | known-vrf-name | all ]

Clears the group entries in the SA cache.

Configuration Examples for MSDP

To configure MSDP peers, some of the optional parameters, and a mesh group, follow these steps for each MSDP peer:

Step 1 Configure the MSDP peering relationship with other routers.

switch# config t
switch(config)# ip msdp peer 192.168.1.10 connect-source ethernet 1/0 remote-as 8
 

Step 2 Configure the optional peer parameters.

switch# config t
switch(config)# ip msdp password 192.168.1.10 my_peer_password_AB
 

Step 3 Configure the optional global parameters.

switch# config t
switch(config)# ip msdp sa-interval 80
 

Step 4 Configure the peers in each mesh group.

switch# config t
switch(config)# ip msdp mesh-group 192.168.1.10 mesh_group_1
 

 

The following example shows how to configure a subset of the MSDP peering that is shown in Figure 1-1.

  • RP 3: 192.168.3.10 (AS 7)
config t
ip msdp peer 192.168.1.10 connect-source ethernet 1/1
ip msdp peer 192.168.2.10 connect-source ethernet 1/2
ip msdp peer 192.168.6.10 connect-source ethernet 1/3 remote-as 9
ip msdp password 192.168.6.10 my_peer_password_36
ip msdp sa-interval 80
ip msdp mesh-group 192.168.1.10 mesh_group_123
ip msdp mesh-group 192.168.2.10 mesh_group_123
ip msdp mesh-group 192.168.3.10 mesh_group_123
 
  • RP 5: 192.168.5.10 (AS 8)
config t
ip msdp peer 192.168.4.10 connect-source ethernet 1/1
ip msdp peer 192.168.6.10 connect-source ethernet 1/2 remote-as 9
ip msdp password 192.168.6.10 my_peer_password_56
ip msdp sa-interval 80
 
  • RP 6: 192.168.6.10 (AS 9)
config t
ip msdp peer 192.168.7.10 connect-source ethernet 1/1
ip msdp peer 192.168.3.10 connect-source ethernet 1/2 remote-as 7
ip msdp peer 192.168.5.10 connect-source ethernet 1/3 remote-as 8
ip msdp password 192.168.3.10 my_peer_password_36
ip msdp password 192.168.5.10 my_peer_password_56
ip msdp sa-interval 80
 

Additional References

For additional information related to implementing MSDP, see the following sections:

Related Documents

Related Topic
Document Title

VDCs

Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 4.2

CLI commands

Cisco Nexus 7000 Series NX-OS Multicast Routing Command Reference, Release 5.x

Configuring Policy Based Routing and MBGP

Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 5.x

Standards

Standards
Title

RFC 4624

Multicast Source Discovery Protocol (MSDP) MIB