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This chapter describes how to configure Multicast Source Discovery Protocol (MSDP) on a Cisco NX-OS switch.
You can use 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” For information about BGP, see the Cisco Nexus 5000 Series NX-OS Unicast Routing Configuration Guide.
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 1 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:
MSDP peers exchange Source-Active (SA) messages that the MSDP software uses to propagate information about active sources. SA messages contain the following information:
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 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 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.
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.
You can define multiple virtual routing and forwarding (VRF) instances. The MSDP configuration applies to the selected VRF.
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 VRFs, see the Cisco Nexus 5000 Series NX-OS Unicast Routing Configuration Guide.
The following table shows the licensing requirements for this feature:
MSDP has the following prerequisites:
Table 1-1 lists the default settings for MSDP parameters.
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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.
Before you can access the MSDP commands, you must enable the MSDP feature.
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Enables the MSDP feature so that you can enter MSDP commands. By default, the MSDP feature is disabled. |
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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.
Ensure that you have installed the LAN Base 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.
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 ]
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.
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Description string for the peer. By default, the peer has no description. |
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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. |
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MD5-shared password key used for authenticating the peer. By default, no MD5 password is enabled. |
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Route-map policy1 for incoming SA messages. By default, all SA messages are received. |
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Route-map policy 1 for outgoing SA messages. By default, all registered sources are sent in SA messages. |
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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 5000 Series NX-OS Unicast Routing Configuration Guide. |
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.
Ensure that you have installed the LAN Base Services license and enabled PIM and MSDP.
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 ]
You can configure the optional MSDP global parameters described in Table 1-3 .
Ensure that you have installed the LAN Base Services license and enabled PIM and MSDP.
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 ]
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.
Ensure that you have installed the LAN Base Services license and enabled PIM and MSDP.
2. ip msdp mesh-group peer-ip-addr mesh-name
3. Repeat Step 2 for each MSDP peer in the mesh.
4. (Optional) show ip msdp mesh-group [ mesh-group ] [ vrf vrf-name | known-vrf-name | all ]
You can restart the MSDP process and optionally flush all routes.
Ensure that you have installed the LAN Base Services license and enabled PIM and MSDP.
4. (Optional) show running-configuration | include flush-routes
To display the MSDP configuration information, perform one of the following tasks:
For detailed information about the fields in the output from these commands, see the Cisco Nexus 5000 Series Command Reference, Cisco NX-OS Releases 4.x, 5.x.
You can display and clear MSDP statistics by using the features in this section.
This section has the following topics:
You can display MSDP statistics using the commands listed in Table 1-4 .
You can clear the MSDP statistics using the commands listed in Table 1-5 .
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.
Step 2 Configure the optional peer parameters.
Step 3 Configure the optional global parameters.
Step 4 Configure the peers in each mesh group.
This example shows how to configure a subset of the MSDP peering that is shown in Figure 1-1.
For additional information related to implementing MSDP, see the following sections:
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Cisco Nexus 5000 Series Command Reference, Cisco NX-OS Releases 4.x, 5.x |
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No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
Table 1-6 lists the release history for this feature.
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