PIX Firewall Software version 6.2 and higher enables you to statically configure multicast routes or use an Internet Group Management Protocol (IGMP) helper address to forward IGMP reports and leave announcements.
This is the multicast support available in this release:
Access list filters can be applied in order to multicast traffic to permit or deny specific protocols and ports.
Network Address Translation (NAT) and Port Address Translation (PAT) can be performed on the multicast packet source addresses only.
Multicast data packets with destination addresses in the 224.0.0.0/24 address range are not forwarded. But, everything else in the 224.0.0.0/8 address range is forwarded.
IGMP packets for address groups within the 224.0.0.0-224.0.0.255 range are not forwarded because these addresses are reserved for protocol use.
NAT is not performed on IGMP packets. When IGMP forwarding is configured, the PIX Firewall forwards the IGMP packets (report and leave) with the IP address of the helper interface as the source IP address.