H3C Technologies H3C S7500E Series Switches - Manual (Page 215)

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Configuring SA Request Messages
By default, upon receiving a new Join message, a router does not send an SA request message to any
MSDP peer; instead, it waits for the next SA message from its MSDP peer. This will cause the receiver
to delay obtaining multicast source information. To enable a new receiver to get the currently active
multicast source information as early as possible, you can configure routers to send SA request
messages to the designated MSDP peers upon receiving a Join message of a new receiver.
Follow these steps to configure SA message transmission and filtering:
To do... Use the command... Remarks
Enter system view system-view —
Enter public instance MSDP view or
VPN instance MSDP view
msdp [ vpn-instance
vpn-instance-name ]
—
Enable the device to send SA request
messages
peer peer-address
request-sa-enable
Optional
Disabled by default
Configure a filtering rule for SA
request messages
peer peer-address
sa-request-policy [ acl
acl-number ]
Optional
SA request messages are not
filtered by default
Before you can enable the device to send SA requests, be sure to disable the SA message cache
mechanism.
Configuring SA Message Filtering Rules
By configuring an SA message creation rule, you can enable the router to filter the (S, G) entries to be
advertised when creating an SA message, so that the propagation of messages of multicast sources is
controlled.
By configuring a filtering rule for receiving or forwarding SA messages, you can enable the router to
filter the (S, G) forwarding entries to be advertised when receiving or forwarding an SA message, so
that the propagation of multicast source information is controlled at SA message reception or
forwarding.
By configuring a TTL threshold for multicast data packet encapsulation in SA messages, you can
control the multicast data packet encapsulation in SA messages and limit the propagation range of SA
messages:
z Before creating an SA message with an encapsulated multicast data packet, the router checks
the TTL value of the multicast data packet. If the TTL value is less than the threshold, the router
does not create an SA message; if the TTL value is greater than or equal to the threshold, the
router encapsulates the multicast data in an SA message and sends the SA message out.