● A multicast router may receive thousands of multicast  （71）  every day fordifferent groups. If a router has no knowledge about the membership status of the  （72）  , itmust broadcast all of these packets. This creates a lot of traffic and consumes  （73）. A bettersolution is to keep a list of groups in the network for which there is at least one loyal member.（74） helps the multicast router create and update this list. For each group, there is one routerthat has the duty of distributing the  （75） packets destined for that group. This means that ifthere are three multicast routers connected to a network, their lists of groupids are mutuallyexclusive. A host or multicast router can have membership in a group.