H3C Technologies H3C SecPath F1000-E - Manual (Page 74)

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• Upon receiving an SA message with an encapsulated multicast data packet, the router decrements
the TTL value of the multicast packet by 1 and then checks 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 out.
Follow these steps to configure a filtering rule for receiving or forwarding SA messages:
To do... Use the command... Remarks
Enter system view system-view —
Enter public network MSDP view msdp —
Configure an SA message creation
rule
import-source [ acl acl-number ]
Required
No restrictions on (S, G) entries by
default
Configure a filtering rule for
receiving or forwarding SA
messages
peer peer-address sa-policy
{ import | export } [ acl
acl-number ]
Required
No filtering rule by default
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, you can enable the SA cache mechanism
to cache (S, G) entries contained in SA messages locally on the router. However, the more (S, G) entries
are cached, the larger memory space of the router is used.
With the SA cache mechanism enabled, when receiving 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 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 effectively against denial of service (DoS) attacks, you can set a limit on the number
of (S, G) entries the router can cache.
Follow these steps to configure the SA message cache:
To do... Use the command... Remarks
Enter system view system-view —
Enter public network MSDP view msdp —
Enable the SA cache mechanism cache-sa-enable
Optional
Enabled by default
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