D-Link DGS-3312SR [180/290] Ip multicast

D-Link DGS-3312SR [180/290] Ip multicast
DGS-3312SR Stackable Gigabit Layer 3 Switch
IP Multicast
ant to receive multicast transmissions need to inform nearby routers that they will
ps that have active members. The information received from
Controlling Multicast Routing on the Switch includes setting up IGMP for IP interfaces, PIM and DVMRP. This chapter
describes how to set these up. For an explanation of how these protocols function, read Appendix C.
IGMP
Computers and network devices that w
become members of a multicast group. The Internet Group Management Protocol (IGMP) is used to communicate this
information. IGMP is also used to periodically check the multicast group for members that are no longer active.
In the case where there is more than one multicast router on a subnetwork, one router is elected as the ‘querier’. This router
then keeps track of the membership of the multicast grou
IGMP is then used to determine if multicast packets should be forwarded to a given subnetwork or not. The router can
check, using IGMP, to see if there is at least one member of a multicast group on a given subnetwork. If there are no
members on a subnetwork, packets will not be forwarded to that subnetwork.
IGMP Versions 1 and 2
Multicast groups allow members to join or leave at any time. IGMP provides the method for members and multicast
routers to communicate when joining or leaving a multicast group.
IGMP version 1 is defined in RFC 1112. It has a fixed packet size and no optional data.
The format of an IGMP packet is shown below:
Figure 4- 80. IGMP Message Format
The IGMP Type codes are shown below:
Type Meaning
0x11 Membership Query (if Group Address is 0.0.0.0)
0x11 Specific Group Membership Query (if Group Address is Present)
0x16 Membership Report (version 2)
0x17 Leave a Group (version 2)
0x12 Membership Report (version 1)
Table 6- 1. IGMP Type Codes
IGMP packets enable multicast routers to keep track of the membership of multicast groups, on their respective
subnetworks. The following outlines what is communicated between a multicast router and a multicast group member
using IGMP.
A host sends an IGMP “re
uters send IGMP queries (to the all-hosts group address: 224.0.0.1) periodically to see whether any group
roup, the router assumes that there are no
port” to join a group
A host will never send a report when it wants to leave a group (for version 1).
A host will send a “leave” report when it wants to leave a group (for version 2).
Multicast ro
members exist on their subnetworks. If there is no response from a particular g
group members on the network.
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