3Com 4800G Series, Configuration Manual

Page: 684 / 1246

684 C
HAPTER
48: MSDP C
ONFIGURATION
Configuring an SA
Message Filtering Rule
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.
In addition to controlling SA message creation, you can also configure filtering
rules for forwarding and receiving SA messages, so as to control the propagation
of multicast source information in the SA messages.
■
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.
■
An SA message with encapsulated multicast data can be forwarded to a
designated MSDP peer only if the TTL value in its IP header exceeds the
threshold. Therefore, you can control the forwarding of such an SA message by
configuring the TTL threshold of the encapsulated data packet.
Follow these steps to configure a filtering rule for receiving or forwarding SA
messages:
Configuring SA Message
Cache
To reduce the time spent in obtaining the multicast source information, you can
have SA messages cached on the router. However, the more SA messages are
cached, the larger memory space of the router is used.
With the SA cache mechanism enabled, when receiving a new Join message, the
router will not send an SA request message to its MSDP peer; instead, it acts as
follows:
■
If there is no SA message in the cache, the router will wait for the SA message
sent by its MSDP peer in the next cycle;
■
If there is an SA message in the cache, the router will obtain the information of
all active sources directly from the SA message and join the corresponding SPT.
To protect the router against denial of service (DoS) attacks, you can configure the
maximum number of SA messages the route can cache.
Follow these steps to configure the SA message cache:
To do… Use the command… Remarks
Enter system view system-view -
Enter 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 minimum TTL
value of multicast packets to
be encapsulated in SA
messages peer peer-address
minimum-ttl ttl-value
Optional
0 by default