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Introduction
The Multicast Source Discovery Protocol (MSDP) allows Rendezvous Points (RP) of different PIM-SM domains to discover and distribute source information for multicast groups. The PIM-SM domains can be of the same or a different Autonomous System (AS). IPriori supports two versions of the MSDP specification: Version 6 (default) and Version 13.
Each MSDP-speaking router in a PIM-SM domain is configured for a MSDP peering relationship with MSDP peers in another domain. A MSDP speaker sends a Source-Active (SA) message to the MSDP peers to indicate this PIM-SM domain has active source for a particular multicast group. SA messages can be filtered in both the inbound and outbound direction through configuring local policy. Each receiving MSDP-speaking RP, for which the sources are appropriate, can join the source-based tree through a PIM-SM join.
The MSDP peering relationship is achieved over a TCP connection, where a list of sources sending to multicast groups is exchanged. The TCP connections between RPs are achieved by the underlying routing system. MSDP uses the AS number configured through the CLI as the local AS. One side of the peering listens on well-known port 639 while the other side performs the active connect. The peer with the higher IP address listens.
A MSDP default peer can be configured in order to accept all SA messages from the default-peer, provided all other RPF-check rules do not match. A RPF check is performed on all incoming SA messages before Inbound policy is applied. When a SA message is received, it is passed through the RPF-check rules and if none of the rules match, then the default-peer (if configured) is used as a last resort to accept the SA message. If no default-peer is configured, then the SA message is discarded.
IPriori provides for the configuration of a mesh-group of any group of MSDP speakers that are fully meshed. A MSDP mesh-group reduces SA flooding by assuming that a mesh-group member does not have to forward SA messages to other group members, because the originator will forward to all group members.
MSDP functionality:
- Eliminates the need for a PIM-SM domain to rely on RPs of another domain
- Eliminates the need for receiver only domains to advertise their group membership globally.
- Saves resources by eliminating the need for global source multicast routing tables.
- Localizes the shared multicast distribution tree to the local domain.
Configuring An MSDP Peer
MSDP SA messages are exchanged between an MSDP speaker and its configured peers. Each MSDP-speaking router in a PIM-SM domain is configured for a MSDP peering relationship with MSDP peers in another domain. The peer's PIM-SM domain can be of the same or a different Autonomous System (AS). The MSDP peering relationship is achieved over a TCP connection, where a list of sources sending to multicast groups is exchanged via SA messages. When configuring a peering relationship with this RP specify the IP address of the peering RP.
The ip msdp peer command, specifying the IP address of the peer, is used to configure a peer for this MSDP speaker. The interface of the MSDP speaker to use as the source IP address for the TCP connection can be specified using the connect-source option.
When an RP is an MSDP peer but not a BGP peer, the system can sometimes specify the wrong AS in statistics. To avoid this problem, the remote-as of the peer can be specified using the remote-as option.
Example 1: The following command specifies RP 192.168.1.3 as a peer for this MSDP speaker and identifies the POS interface 1/1/1 as the source connection:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#ip msdp peer 192.168.1.3 connect-source pos 1/1/1
router(config)#end
router#
Example 2: The following command deletes the MSDP peer relationship between this speaker and IP address 192.168.1.3:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#no ip msdp peer 192.168.1.3
router(config)#end
router#Configuring an IP MSDP Default Peer
A MSDP default peer is configured in order to accept all SA messages from the default-peer, provided all other RPF-check rules do not match. A RPF check is performed on all incoming SA messages before Inbound policy is applied. When a SA message is received, it is passed through the RPF-check rules and if none of the rules match, then the default-peer (if configured) is used as a last resort to accept the SA message. If no default-peer is configured, then the SA message is discarded.
If more than one MSDP default peer is configured on a speaker, all SA messages received from the first default peer identified in the configuration file are accepted. Should the first MSDP default peer shutdown, all SA messages received from the second default peer listed in the configuration are then accepted.
To configure an IP MSDP default peer for this speaker, use the ip msdp default-peer command specifying the IP address of the default peer. A prefix-list can be applied to the default peer for purposes of filtering policy.
Configuring Connect Retry Timer for MSDP Peering Sessions
IPriori provides for the configuration of a connection retry timer for all MSDP peering sessions. Use the ip msdp timer command in configuration mode to set the amount of time in seconds between connection retry for all MSDP peering sessions.
Example 1: The following command sets the MSDP retry timer to 25 seconds:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#ip msdp timer 25
router(config)#end
router#
Example 2: The following command resets the MSDP retry timer to the default value:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#no ip msdp timer
router(config)#end
router#
Configuring an Interface IP Address Originator ID
The default SA message originator ID is the RP address of the originator. The originator address in the SA message can be configured to use the interface IP address of the originator.
Use the ip msdp originator-id command to specify the interface from which the originator ID IP address will be derived.
Use the no ip msdp originator-id command to use the RP address for this speaker as the originator ID for SA messages.
Example 1: The following command configures interface pos 1/1/1 as the originator ID for SA messages sent by this speaker:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#ip msdp originator-id pos 1/1/1
Example 2: The following command removes pos 1/1/1 as the originator ID for SA messages sent by this speaker, reverting the originator ID back to the RP address:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#no msdp originator-id pos 1/1/1
Configuring a MSDP Peer Description
For purposes of ease of MSDP peer identification, a descriptive text of up to 255 characters can be associated with a MSDP peer. Use the ip msdp description peer-address command to associate a description of up to 255 ASCII characters with the specified MSDP peer. Use the no ip msdp description peer-address command to remove the description associated with the specified MSDP peer. Configured MSDP peer descriptions are displayed using the show ip msdp peer command.
Example 1: The following command associates the First peer description to MSDP peer 10.10.10.10:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#ip msdp description 10.10.10.10 First peer
router(config)#end
router#
Example 2: The following command removes the description associated with MSDP peer 10.10.10.10:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#no ip msdp description 10.10.10.10
router(config)#end
router#
Resetting an IP MSDP Peer
Resetting the IP MSDP peer closes the current TCP connection between this MSDP speaker and the specified peer resets the MSDP statistics for the connection and clears the input and output queues to and from the MSDP peer. Once all cleanup work is complete, the connection is automatically reestablished. To reset the MSDP TCP connection to the specified MSDP peer for this speaker, use the clear ip msdp peer command, specifying the IP address of the MSDP peer.
To delete the MSDP peer configuration between this speaker and a peer, use the no ip msdp peer command, specifying the IP address of the MSDP peer.
Example: The following command resets the TCP connection between this MSDP speaker and MSDP peer 192.168.1.3:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#clear ip msdp peer 192.168.1.3
Configuring an MSDP Mesh-Group
A MSDP mesh-group reduces SA flooding by assuming that a mesh-group member does not have to forward SA messages to other group members, because the originator, that is also a mesh-group member, will forward to all group members. MSDP mesh groups can be created out of any group of a domain's fully meshed MSDP speakers.
If a mesh-group member receives a SA message from an MSDP peer that is also a member of the mesh-group, the group member accepts the SA and forwards it to all peers that are not a member of the mesh-group. If a mesh-group member receives a SA message from a MSDP peer that is not a member of the mesh-group, and the SA message passes the RPF check, then the member forwards the SA message to all members of the mesh-group.
Use the ip msdp mesh-group command to configure the specified MSDP peer as a member of the named mesh-group.
Use the no ip mdsp mesh-group command to remove the specified MSDP peer from the named mesh-group.
Example 1: The following command configures MSDP speaker 10.10.10.10 to be a member of mesh-group group1:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#ip msdp mesh-group group1 10.10.10.10
router(config)#end
router#
Example 2: The following command removes MSDP speaker 10.10.10.10 from mesh-group group1:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#no ip msdp mesh-group group1 10.10.10.10
router(config)#end
router#
Configuring the MSDP Redistribute Filter
The (S,G) multicast routing table entries advertised in SA messages that originate from this MSDP speaker can be filtered using the redistribute filter. If no redistribute filter is configured, all local sources are advertised that send to groups for which this router is a RP. If the redistribute filter is configured with no keywords specified, no local sources are advertised for this MSDP speaker. The redistribute filter can be configured using an extended access-list or a route map.
Use the ip msdp redistribute command to filter all local sourced multicast groups from advertising for this MSDP speaker.
Use the ip msdp redistribute list command to filter local sourced multicast advertising based upon the specified access-list.
Use the ip msdp redistribute route-map command to filter local sourced multicast advertising based upon the specified route-map.
Use the no ip msdp redistribute command to remove previously configured redistribute filtering for this MSDP speaker.
Example 1: The following command filters all locally sourced multicast advertising for this MSDP speaker:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#ip msdp redistribute
router(config)#end
router#
Example 2: The following command filters locally sourced multicast advertising based upon the access-list acl1:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#ip msdp redistribute list acl1
router(config)#end
router#
Configuring Inbound and Outbound SA Message Filters
The SA filter provides for the configuration of both an incoming and outgoing filter list for SA messages received from and sent to the specified MSDP peer. Filtering of SA messages in either direction can be configured using an access-list or route-map. If no SA filter is configured, no incoming or outgoing SA messages are filtered.
When using a route-map, if all match criteria are true, a permit keyword from the route-map will pass routes through the filter. A deny keyword will filter routes specified in the entry.
Use the ip msdp sa-filter in ipaddress command to filter all incoming SA messages from the specified MSDP peer.
Use the ip msdp sa-filter in ipaddress list command to filter incoming SA messages from the specified MSDP peer, based upon the contents of the specified access-list.
Use the ip msdp sa-filter in ipaddress route-map command to filter incoming SA messages from the specified MSDP peer, based upon the contents of the specified route-map.
Use the ip msdp sa-filter out ipaddress command to filter all outbound SA messages to the specified MSDP peer.
Use the ip msdp sa-filter out ipaddress list command to filter outbound SA messages to the specified MSDP peer, based upon the contents of the specified access-list.
Use the ip msdp sa-filter out ipaddress route-map command to filter outbound SA messages to the specified MSDP peer, based upon the contents of the specified route-map.
Use the no version of each of these commands to remove the incoming or outbound SA filtering, specifying an access-list or route-map if applicable.
Example 1: The following command filters incoming SA messages to this speaker from MSDP peer 10.10.10.10 based upon the contents of the acl1 access-list:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#ip msdp sa-filter in 10.10.10.10 list acl1
router(config)#end
router#
Example 2: The following command removes the outbound filter of all SA messages from this speaker to the MSDP peer 10.10.10.10:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#no ip msdp sa-filter 10.10.10.10
Clearing the Source Active Cache
A MSDP speaker must cache SA messages. Caching allows pacing of MSDP messages as well as reduces join latency for new receivers. As part of problem recovery or to clear stale SA entries, the SA cache can be cleared globally, by multicast group address or by multicast name.
Use the clear ip msdp sa-cache command to globally clear the SA cache for this router.
Use the clear ip msdp sa-cache multicastGroup command, specifying the multicast group to clear a subset of the SA cache.
Example 1: The following command clears the global SA cache for this router:
router#clear ip msdp sa-cache
router#
Example 2: The following command clears the SA cache for the multicast group group1:
router#clear ip msdp sa-cache group1
router#
Configuring a Source Active Request Filter
A MSDP speaker may accept SA requests from other MSDP peers. When an MSDP speaker receives an SA request message for a group range, it responds with an SA response containing a set of SA entries for all active sources in its SA cache, sending to the group requested in the SA request message. By default all SA request messages received by a MSDP speaker are honored. A MSDP speaker can be configured to send SA response messages to a filtered subset or none of the speaker's MSDP peers when a new joiner from a group becomes active.
Use the ip msdp filter-sa-request ip-address command to configure a SA request filter for this MSDP speaker. If no access-list is specified, all SA requests are filtered from the specified peer for this MSDP speaker.
Use the ip msdp filter-sa-request ip-address list command to filter SA requests from access-list multicast group entries for the specified MSDP peer.
Use the no ip msdp filter-sa-request ip-address command to remove any configured filtering of SA request messages for the specified MSDP peer for this MSDP speaker.
Example 1: The following command will filter out all SA request messages from MSDP peer 10.10.10.10 for this speaker:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#ip msdp filter-sa-request 10.10.10.10
router(config)#end
router#
Example 2: The following command will filter out SA request messages for multicast group addresses specified in access-list acl1 for MSDP peer 10.10.10.10:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#ip msdp filter-sa-request 10.10.10.10 list acl1
Example 3: The following command will remove the SA request filter for MSDP peer 10.10.10.10:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#no ip msdp filter-sa-request 10.10.10.10
router(config)#
Configuring a MSDP TTL Threshold
Time-To-Live (TTL) provides a means to limit the number of hops a packet can take before being dropped. By default, multicast data packets in SA messages are sent to an MSDP peer are forwarded providing the TTL value of the packet is greater than 0. This is standard TTL behavior. The MSDP TTL threshold provides for setting a higher threshold that must be met for a packet to be forwarded. If the MSDP TTL threshold is set to 2, than incoming multicast packets sent in SA messages must have a TTL value of 2 or greater to be forwarded in the SA message. In this case, data packets with a TTL value of 1 or 0 would be dropped.
Use the ip msdp ttl-threshold command to set a TTL threshold that must be met by incoming packets for them to be forwarded in an SA message to an MSDP peer of this speaker.
Use the no msdp ttl-threshold command to reset the MSDP TTL threshold to 0 for this MSDP speaker.
Example 1: The following command sets the MSDP TTL threshold to 2 for SA message data packets bound for MSDP peer 10.10.10.10:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#ip msdp ttl-threshold 10.10.10.10 2
Example 2: The following command resets the MSDP TTL threshold to 0 for SA message data packets bound for MSDP peer 10.10.10.10:
router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#no ip msdp ttl-threshold 10.10.10.10
Display Information about MSDP
MSDP includes a variety of commands to display information about multicast traffic. The commands are:
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Copyright © 2004
Avici Systems Inc.
Avici® and TSR®
is a registered trademark of Avici Systems Inc.
IPriori™, Composite Links™, SSR™, QSR, and NSR® are
trademarks of Avici Systems Inc.
Source
File Name: MSDP.fm
HTML File Name: MSDP.html
Last Updated: 12/19/04 at 16:12:06