IGMP Proxy

Internet Group Management Protocol (IGMP)

A IGMP Proxy to send IGMP host messages on behalf of a connected client. The configuration must define one upstream interface, and one or more downstream interfaces. If multicast traffic originates outside the upstream subnet, the “alt-subnet” option can be used in order to define legal multicast sources.

simple example:

Interface eth1 LAN is behind NAT. In order to subscribe 10.0.0.0/23 subnet multicast which is in eth0 WAN we need igmp-proxy.

# show protocols igmp-proxy
interface eth0 {
    alt-subnet 10.0.0.0/23
    role upstream
}
interface eth1 {
    role downstream
}