Dell PowerConnect 8100 User's Configuration Guide - Page 697
What Is IGMP Snooping?, IGMP Membership queries
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What Is IGMP Snooping? IGMP snooping allows the switch to snoop on IGMP exchanges between hosts and multicast routers. The IGMP snooping feature complies with RFC 4541. When a switch "sees" an IGMP report from a host for a given multicast address, the switch adds the host's interface/VLAN to the L2 multicast group forwarding table and floods the report to all ports in the VLAN. When the switch sees a leave message for the group, it removes the host interface/VLAN from the L2 multicast group forwarding table. IGMP snooping learns about multicast routers by listening for the following messages: • IGMP Membership queries • PIMv1 hellos • PIMv2 hellos • DVMRP probes Group addresses that fall into the range 224.0.0.x are never pruned by IGMP snooping-they are always flooded to all ports in the VLAN. Note that this flooding is based on the IP address, not the corresponding 01-00-5e-00-00-xx MAC address. When a multicast router is discovered, its interface is added to the interface distribution list for all multicast groups in the VLAN. If a switch is connected to a multicast source and no client, the switch filters the traffic from that group to all interfaces in the VLAN. If the switch sees an IGMP join from a host in the same VLAN, then it forwards the traffic to the host. Likewise, if the switch sees a multicast router in the VLAN, it forwards the group to the multicast router and does not flood in the VLAN. There is a user option to cause the switch to flood multicast sources in the VLAN if no multicast clients are present. This option should be enabled when deploying the switch in scenarios, such as FCoE/FIP snooping, where it is desirable to flood L2 control plane multicast messages that do not utilize well-known multicast addresses. By default, multicast routers are aged out every five minutes. The user can control whether or not multicast routers age out. If all multicast routers age out, the switch floods the VLAN with the multicast group. Configuring L2 Multicast Features 697
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-
1,189
-
1,190
-
1,191
-
1,192
-
1,193
-
1,194
-
1,195
-
1,196
-
1,197
-
1,198
-
1,199
-
1,200
-
1,201
-
1,202
-
1,203
-
1,204
-
1,205
-
1,206
-
1,207
-
1,208
-
1,209
-
1,210
-
1,211
-
1,212
-
1,213
-
1,214
-
1,215
-
1,216
-
1,217
-
1,218
-
1,219
-
1,220
-
1,221
-
1,222
-
1,223
-
1,224
-
1,225
-
1,226
-
1,227
-
1,228
-
1,229
-
1,230
-
1,231
-
1,232
-
1,233
-
1,234
-
1,235
-
1,236
-
1,237
-
1,238
-
1,239
-
1,240
-
1,241
-
1,242
-
1,243
-
1,244
-
1,245
-
1,246
-
1,247
-
1,248
-
1,249
-
1,250
-
1,251
-
1,252
-
1,253
-
1,254
-
1,255
-
1,256
-
1,257
-
1,258
-
1,259
-
1,260
-
1,261
-
1,262
-
1,263
-
1,264
-
1,265
-
1,266
-
1,267
-
1,268
-
1,269
-
1,270
-
1,271
-
1,272
-
1,273
-
1,274
-
1,275
-
1,276
-
1,277
-
1,278
-
1,279
-
1,280
-
1,281
-
1,282
-
1,283
-
1,284
-
1,285
-
1,286
-
1,287
-
1,288
-
1,289
-
1,290
-
1,291
-
1,292
-
1,293
-
1,294