Configuring TTL

Configuring TTL
TTL threshold configuration is done to limit the boundary of scope of the IP multicast network.
As you learned earlier in this chapter, limiting the scope of a multicast network is based on the
TTL value in the multicast packet. Because this command is used to create a boundary, it must
be executed on each border interface.
The default value for the TTL threshold is zero. The value can be changed with the ip
multicast ttl-threshold ttl command. The syntax is straightforward, and the ttl value
that is used is up to the discretion of the network administrator. The range of valid values for
this option is between 0 and 255. However, the value should be high enough to stop multicast
packets from exiting the interface. Here is an example:
Terry_3640#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Terry_3640(config)#interface FastEthernet0/0
Terry_3640(config-if)#ip multicast ttl-threshold 230
Terry_3640(config-if)#^Z
Terry_3640#
!
interface FastEthernet0/0
ip address 172.16.5.1 255.255.255.0
no ip directed-broadcast
ip pim sparse-dense-mode
ip multicast ttl-threshold 230
no ip route-cache
Configuring IP Multicast Routing 629
no ip mroute-cache
full-duplex
!