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threshold, the router encapsulates the multicast data in an SA message and sends the SA
message.
•
After receiving an SA message with an encapsulated multicast data packet, the router
decreases the TTL value of the multicast packet by 1 and then examines the TTL value. If the
TTL value is less than the threshold, the router does not forward the SA message to the
designated MSDP peer. If the TTL value is greater than or equal to the threshold, the router
re-encapsulates the multicast data in an SA message and sends the SA message.
To configure a filtering rule for receiving or forwarding SA messages:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter public network MSDP
view or VPN instance MSDP
view.
msdp
[
vpn-instance
vpn-instance-name
]
N/A
3.
Configure an SA message
creation rule.
import-source
[
acl
acl-number
]
No restrictions on (S, G) entries
by default.
4.
Configure a filtering rule for
receiving or forwarding SA
messages.
peer
peer-address
sa-policy
{
import
|
export
} [
acl
acl-number
]
No filtering rule by default.
5.
Configure the TTL threshold
for multicast data packet
encapsulation in SA
messages.
peer
peer-address
minimum-ttl
ttl-value
Optional.
0 by default.
Configuring the SA cache mechanism
To reduce the time spent in obtaining the multicast information, enable the SA cache mechanism to
cache (S, G) entries contained in SA messages locally on the router. However, caching (S, G) entries
uses memory space on the router.
When the SA cache mechanism is enabled and the router receives a new (*, G) join message, the
router searches its SA cache first.
•
If the corresponding (S, G) entry does not exist in the cache, the router waits for the SA
message that its MSDP peer will send in the next cycle.
•
If the corresponding (S, G) entry exists in the cache, the router joins the corresponding SPT
rooted at S.
To protect the router against denial of service (DoS) attacks, you can set a limit on the number of (S,
G) entries that the router can cache.
To configure the SA message cache:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter public network MSDP view or
VPN instance MSDP view.
msdp
[
vpn-instance
vpn-instance-name
]
N/A
3.
Enable the SA cache mechanism.
cache-sa-enable
Optional.
Enabled by default.
4.
Configure the maximum number of
(S, G) entries learned from the
specified MSDP peer that the router
can cache.
peer
peer-address
sa-cache-maximum
sa-limit
Optional.
8192 by default.
