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Configuring IP Multicast Routing
Information About Cisco’s Implementation of IP Multicast Routing
In
, Switch A routed uplink port 25 is connected to the router and PIM stub routing is enabled on
the VLAN 100 interfaces and on Host 3. This configuration allows the directly connected hosts to receive traffic from
multicast source 200.1.1.3. See
Configuring PIM Stub Routing, page 691
for more information.
Figure 86
PIM Stub Router Configuration
IGMP Helper
PIM stub routing moves routed traffic closer to the end user and reduces network traffic. You can also reduce traffic by
configuring a stub router (switch) with the IGMP helper feature.
You can configure a stub router (switch) with the
igmp helper help-address
interface configuration command to enable
the switch to send reports to the next-hop interface. Hosts that are not directly connected to a downstream router can
then join a multicast group sourced from an upstream network. The IGMP packets from a host wanting to join a multicast
stream are forwarded upstream to the next-hop device when this feature is configured. When the upstream central router
receives the helper IGMP reports or leaves, it adds or removes the interfaces from its outgoing interface list for that group.
For complete syntax and usage information for the
ip igmp
helper-address
command, see the
Cisco IOS IP Multicast
Command Reference
.
Auto-RP
This proprietary feature eliminates the need to manually configure the RP information in every router and multilayer switch
in the network. For Auto-RP to work, you configure a Cisco router or multilayer switch as the mapping agent. It uses IP
multicast to learn which routers or switches in the network are possible candidate RPs to receive candidate RP
announcements. Candidate RPs periodically send multicast RP-announce messages to a particular group or group range
to announce their availability.
Mapping agents listen to these candidate RP announcements and use the information to create entries in their
Group-to-RP mapping caches. Only one mapping cache entry is created for any Group-to-RP range received, even if
multiple candidate RPs are sending RP announcements for the same range. As the RP-announce messages arrive, the
mapping agent selects the router or switch with the highest IP address as the active RP and stores this RP address in the
Group-to-RP mapping cache.
Mapping agents periodically multicast the contents of their Group-to-RP mapping cache. Thus, all routers and switches
automatically discover which RP to use for the groups they support. If a router or switch fails to receive RP-discovery
messages and the Group-to-RP mapping information expires, it switches to a statically configured RP that was defined
with the
ip pim rp-address
global configuration command. If no statically configured RP exists, the router or switch
changes the group to dense-mode operation.
Multiple RPs serve different group ranges or serve as hot backups of each other.
S
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200.1.1.
3
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ter
3
.1.1.2.255.255.255.0
S
witch
A
Ho
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t 1
Ho
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t 2
VLAN 100
Ho
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3
Port 25
Port 20
202
3
61
Summary of Contents for IE 4000
Page 12: ...8 Configuration Overview Default Settings After Initial Switch Configuration ...
Page 52: ...48 Configuring Interfaces Monitoring and Maintaining the Interfaces ...
Page 108: ...104 Configuring Switch Clusters Additional References ...
Page 128: ...124 Performing Switch Administration Additional References ...
Page 130: ...126 Configuring PTP ...
Page 140: ...136 Configuring CIP Additional References ...
Page 146: ...142 Configuring SDM Templates Configuration Examples for Configuring SDM Templates ...
Page 192: ...188 Configuring Switch Based Authentication Additional References ...
Page 244: ...240 Configuring IEEE 802 1x Port Based Authentication Additional References ...
Page 298: ...294 Configuring VLANs Additional References ...
Page 336: ...332 Configuring STP Additional References ...
Page 408: ...404 Configuring DHCP Additional References ...
Page 450: ...446 Configuring IGMP Snooping and MVR Additional References ...
Page 490: ...486 Configuring SPAN and RSPAN Additional References ...
Page 502: ...498 Configuring Layer 2 NAT ...
Page 770: ...766 Configuring IPv6 MLD Snooping Related Documents ...
Page 930: ...926 Configuring IP Unicast Routing Related Documents ...
Page 976: ...972 Configuring Cisco IOS IP SLAs Operations Additional References ...
Page 978: ...974 Dying Gasp ...
Page 990: ...986 Configuring Enhanced Object Tracking Monitoring Enhanced Object Tracking ...
Page 994: ...990 Configuring MODBUS TCP Displaying MODBUS TCP Information ...
Page 996: ...992 Ethernet CFM ...
Page 1066: ...1062 Using an SD Card SD Card Alarms ...