Caching Source-Active State - Cisco WS-C3550-12G Software Configuration Manual

Configuring MSDP
Command
Step 3 ip prefix-list name [description string] |
seq number {permit | deny} network
length
Step 4
ip msdp description {peer-name |
peer-address} text
Step 5 end
Step 6
show running-config
Step 7
copy running-config startup-config
To remove the default peer, use the no ip msdp default-peer global configuration command.
This example shows a partial configuration of Router A and Router C in
have more than one customer (like the customer in
MBGP). In that case, they might have similar configurations. That is, they accept SAs only from a
default peer if the SA is permitted by the corresponding prefix list.
Router A
Router(config)# ip msdp default-peer 10.1.1.1
Router(config)# ip msdp default-peer 10.1.1.1 prefix-list site-a
Router(config)# ip prefix-list site-b permit 10.0.0.0/8
Router C
Router(config)# ip msdp default-peer 10.1.1.1 prefix-list site-a
Router(config)# ip prefix-list site-b permit 10.0.0.0/8

Caching Source-Active State

By default, the multilayer switch does not cache source/group pairs from received SA messages. When
the switch forwards the MSDP SA information, it does not store it in memory. Therefore, if a member
joins a group soon after a SA message is received by the local RP, that member needs to wait until the
next SA message to hear about the source. This delay is known as join latency.
If you want to sacrifice some memory in exchange for reducing the latency of the source information,
you can configure the switch to cache SA messages.
Catalyst 3550 Multilayer Switch Software Configuration Guide
25-6
Purpose
(Optional) Create a prefix list using the name specified in Step 2.
• (Optional) For description string, enter a description of up to 80
characters to describe this prefix list.
• For seq number, enter the sequence number of the entry. The range
is 1 to 4294967294.
• The deny keyword denies access to matching conditions.
• The permit keyword permits access to matching conditions.
• For network length, specify the network number and length (in bits)
of the network mask that is permitted or denied.
(Optional) Configure a description for the specified peer to make it
easier to identify in a configuration or in show command output.
By default, no description is associated with an MSDP peer.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Figure
Chapter 25
Figure 25-2. Each of these ISPs
25-2) who use default peering (no BGP or
Configuring MSDP
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