Configuring IGMP Limit
Context
As defined in multicast protocols, group members can join or leave a group anytime, anywhere, and the number of members in a group is unlimited. If too many users stream videos at the same time, a large amount of bandwidth is consumed, degrading the forwarding performance of the multicast device. The IGMP limit function solves this problem by restricting the number of multicast groups allowed in the system, in a virtual private network (VPN) instance, and on an interface. This allows users who have joined multicast groups to stream high-quality videos. When the router receives an IGMP Report message and needs to create a new IGMP entry, it checks whether the number of IGMP entries exceeds the limit. If not, the router creates the IGMP entry and forwards multicast data to the multicast group.
The global IGMP limit restricts the number of entries on all interfaces. The IGMP limit configured in a VPN instance restricts the number of IGMP entries in the VPN instance. The IGMP limit configured on an interface restricts the number of IGMP entries on the interface.
- Counts each (*, G) entry as one entry.
- Counts each (S, G) entry as one entry.
- Counts each (*, G) entry established with IGMP SSM mapping as one entry but does not count (S, G) entries converted from (*, G) entries.
To apply global, VPN-based, and interface-based IGMP limits together on a switch, you are advised to set the IGMP limit values following this rule: global IGMP limit value > IGMP limit value in a VPN instance > IGMP limit value on an interface.