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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 34 Configuring IP Multicast Routing
Configuring Optional Multicast Routing Features
multicast packets with an initial TTL value set to 99. The engineering and marketing departments have
set a TTL threshold of 40 at the perimeter of their networks; therefore, multicast applications running
on these networks can prevent their multicast transmissions from leaving their respective networks.
Figure 34-11 TTL Boundaries
Beginning in privileged EXEC mode, follow these steps to change the default TTL threshold value:
To return to the default TTL setting, use the no ip multicast ttl-threshold interface configuration
command.
45153
Company XYZ
TTL threshold = 40
Engineering
TTL threshold = 40
TTL threshold = 100
Marketing
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Enter interface configuration mode, and specify the interface to be
configured.
Step 3
ip multicast ttl-threshold ttl-value Configure the TTL threshold of packets being forwarded out an
interface.
The default TTL value is 0 hops, which means that all multicast packets
are forwarded out the interface. The range is 0 to 255.
Only multicast packets with a TTL value greater than the threshold are
forwarded out the interface.
You should configure the TTL threshold only on routed interfaces at the
perimeter of the network.
Step 4
end Return to privileged EXEC mode.
Step 5
show running-config Verify your entries.
Step 6
copy running-config startup-config (Optional) Save your entries in the configuration file.
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