Using Ttl To Limit The Multicast Data Sent In Sa Messages; Controlling Source Information That Your Switch Receives - Cisco IE-4000 Software Configuration Manual

Configuring MSDP
Configuring MSDP
To remove the filter, use the no ip msdp sa-filter out {ip-address | name} [list access-list-number] [route-map
map-tag] global configuration command.
EXAMPLE
This example shows how to allow only (S,G) pairs that pass access list 100 to be forwarded in an SA message to the
peer named switch.cisco.com:
Switch(config)# ip msdp peer switch.cisco.com connect-source gigabitethernet0/1
Switch(config)# ip msdp sa-filter out switch.cisco.com list 100
Switch(config)# access-list 100 permit ip 171.69.0.0 0.0.255.255 224.20 0 0.0.255.255

Using TTL to Limit the Multicast Data Sent in SA Messages

You can use a TTL value to control what data is encapsulated in the first SA message for every source. Only multicast
packets with an IP-header TTL greater than or equal to the ttl argument are sent to the specified MSDP peer. For
example, you can limit internal traffic to a TTL of 8. If you want other groups to go to external locations, you must send
those packets with a TTL greater than 8.
Follow this procedure to establish a TTL threshold. This procedure is optional.
DETAILED STEPS
Command
1. configure terminal
2. ip msdp ttl-threshold {ip-address |
name} ttl
3. end
4. show running-config
5. copy running-config
startup-config
To return to the default setting, use the no ip msdp ttl-threshold {ip-address | name} global configuration command.
EXAMPLE
The following example shows how to configure a TTL threshold of 8 hops:
Switch(config)# ip msdp ttl-threshold 192.168.1.5 8

Controlling Source Information that Your Switch Receives

By default, the switch receives all SA messages that its MSDP RPF peers send to it. However, you can control the source
information that you receive from MSDP peers by filtering incoming SA messages. In other words, you can configure the
switch to not accept them.
You can perform one of these actions:
Table 0-6
Purpose
Enter global configuration mode.
Limit which multicast data is encapsulated in the first SA
message to the specified MSDP peer.

For ip-address | name, enter the IP address or name of the
MSDP peer to which the TTL limitation applies.

For ttl, enter the TTL value. The default is 0, which means
all multicast data packets are forwarded to the peer until
the TTL is exhausted. The range is 0 to 255.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
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