The invention provides a method and device for transmitting
multicast messages, and is applied to NAT (
Network Address Transform) equipment. The method comprises the following steps of: A. receiving messages from each side interface of a
private network of the NAT equipment, and identifying the
multicast messages according to the destination addresses of the messages and going to a step B; B. receiving the
static mapping relationship between an IP (
Internet Protocol) address of the
private network and an
IP address of a
public network issued by an administrator and storing in a
static mapping relationship table; and C. according to a source
IP address carried by the
multicast messages, finding the
static mapping relationship table, if finding a corresponding public
IP address, then converting the source IP address of the multicast messages into the IP address of the
public network and then sending out from an interface of the
public network, otherwise discarding the multicast messages. According to the method and the device provided by the invention , the
processing characteristics of the NAT equipment for the messages are fully considered, although the configuration is needed, the transformation of the equipment is very small, the overall implementation is simple, and the cost for transformation of the network is extremely low.