3Com 5500 SI - Switch - Stackable, Configuration Manual

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Configuring SA Message Transmission 595
Configuring a Rule for
Filtering Received and
Forwarded SA Messages
Besides the creation of source information, controlling multicast source information
allows you to control the forwarding and reception of source information. You can
control the reception of SA messages using the MSDP inbound filter (corresponding
to the
import keyword); you can control the forwarding of SA messages by using
either the MSDP outbound filter (corresponding to the export argument) or the TTL
threshold. By default, an MSDP peer receives and forwards all SA messages.
MSDP inbound/outbound filter implements the following functions:
■
Filtering out all (S, G) entries
■
Receiving/forwarding only the SA messages permitted by advanced ACL rules
An SA message carrying encapsulated data can reach the specified MSDP peer
outside the domain only when the TTL in its IP header exceeds the threshold;
therefore, you can control the forwarding of SA messages that carry encapsulated
data by configuring the TTL threshold.
Configuring SA Message
Cache
With the SA message caching mechanism enabled on the router, the group that a
new member subsequently joins can obtain all active sources directly from the SA
cache and join the corresponding SPT source tree, instead of waiting for the next SA
message.
You can configure the number of SA entries cached in each MSDP peer on the router
by executing the following command, but the number must be within the system
limit. The system sets the maximum number of SA messages cached in each MSDP
peer and the maximum number of SA messages cached in all MSDP peers on the
router; these thresholds must not exceed the system limits. To protect a router against
Deny of Service (DoS) attacks, you can manually configure the maximum number of
SA messages cached on the router. Generally, the configured number of SA messages
cached should be less than the system limit.
Table 651: Configure a rule for filtering received and forwarded SA messages
Operation Command Description
Enter system view system-view -
Enter MSDP view msdp -
Configure the filtering list for
receiving or forwarding SA
messages from the specified
MSDP peer peer peer-address sa-policy {
import | export } [ acl
acl-number ]
Optional
By default, no filtering is
imposed on SA messages to be
received or forwarded, namely all
SA messages from MSDP peers
are received or forwarded
.
Configure the minimum TTL
for the multicast packets sent
to the specified MSDP peer peer peer-address
minimum-ttl ttl-value
Optional
By default, the value of TTL
threshold is 0.
Table 652 Configure SA message cache
Operation Command Description
Enter system view system-view -
Enter MSDP view msdp -
Enable SA message
caching mechanism cache-sa-enable Optional
By default, the SA message caching
mechanism is enabled.