IP Multicast in a WAN
IP Multicast WAN Configuration
There are recommended MSDP filters that should be applied if the network is connected to native IP Multicast on the Internet. The MSDP filters are used to reduce the excessive amount of (S, G) state that is passed between Internet MSDP peers.
For more information about MSDP filters, see: ftp://ftpeng.cisco.com/ipmulticast/config-notes/msdp-sa-filter.txt
IGMP Snooping and CGMP
The topology shown in Figure 5-1 uses CGMP in the branch office switches. CGMP is a better option than IGMP snooping for low-end switches without special hardware.
To take advantage of CGMP, CGMP support must be enabled on the locally attached branch router. The branch office switches in this design scenario are Catalyst 3524-PWR XLs. The Catalyst 3524 supports only CGMP, which is on by default.
Following is the CGMP configuration for “leftrtr.”
ip multicast-routing ! interface FastEthernet0/0.20 ip pim sparse-mode ip cgmp ! interface FastEthernet0/0.120 ip pim sparse-mode ip cgmp
Enable CGMP on the router interface. PIM must be enabled prior to CGMP being enabled.
CGMP operation between the switch and router can be verified using the show cgmp, as shown below:
left 3524#show cgmp CGMP is running. CGMP Fast Leave is not running. CGMP Allow reserved address to join GDA . Default router timeout is 300 sec. _
IGMP MAC Address -----------------
MAC address and port associated with attached router.
Cisco AVVID Network Infrastructure IP Multicast Design