3Com Switch 4800G 24-Port Configuration Manual page 683

Configuring SA Request
Messages
c
If the source-side RP is enabled to encapsulate register messages in SA messages,
when there is a multicast packet to deliver, the source-side RP encapsulates a
register message containing the multicast packet in an SA message and sends it
out. After receiving the SA message, the remote RP decapsulates the SA message
and delivers the multicast data contained in the register message to the receivers
along the RPT.
The MSDP peers deliver SA messages to one another. Upon receiving an SA
message, a router performs RPF check on the message. If the router finds that the
remote RP address is the same as the local RP address, it will discard the SA
message. In the Anycast RP application, however, you need to configure RPs with
the same IP address on two or more routers in the same PIM-SM domain, and
configure these routers as MSDP peers to one another. Therefore, a logic RP
address (namely the RP address on the logic interface) that is different from the
actual RP address must be designated for SA messages so that the messages can
pass the RPF check.
Follow these steps to configure the SA message content:
To do...
Enter system view
Enter MSDP view
Enable encapsulation of a
register message
Configure the interface
address as the RP address in
SA messages
By default, upon receiving a new Join message, a router does not send an SA
request message to its designated 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...
Enter system view
Enter MSDP view
Enable the device to send SA
request messages
Configure a filtering rule for
SA request messages
CAUTION: Before you can enable the device to send SA requests, be sure to
disable the SA message cache mechanism.
Configuring SA Messages Related Parameters
Use the command...
system-view
msdp
encap-data-enable
originating-rp interface-type
interface-number
Use the command...
system-view
msdp
peer peer-address
request-sa-enable
peer peer-address
sa-request-policy [ acl
acl-number ]
683
Remarks
-
-
Optional
Disabled by default
Optional
PIM RP address by default
Remarks
-
-
Optional
Disabled by default
Optional
SA request messages are not
filtered by default