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Agenda

Multicast addressing (L2/L3)IGMPv2IGMPv3IGMP Snooping & VerificationIntro to multicast routing Source Vs. Core-based TreesPIM Sparse-Mode What is multicast State Mcast state rules/PIM JoinsPIM Registration ProcessPIM SwitchoverVerifying PIM OperationsNote : Start your address from 226 to 231 , others are reservedLayer 3 Multicasting AddressingClass D IP address = high order 4 bits are Always 1110 | Multicast Group ID IP multicast group addresses 224.0.0.0 239.255.255.255Special reserved group addresses : 224.0.0.0 - 224.0.0.255224.0.0.1 All systems on this subnet224.0.0.2 All routers on this subnet224.0.0.13 All PIM routers..Note: 01 00 5e the destination mac address Layer 2 Multicast Addressing

In the world of multicast destination mac address are derived from destination ip Address , source mac address is always unicast mac address, so destination mac Address remains the same throughout.

Layer 2 Multicast Addressing

EXAMPLE : Layer 3 to Layer 2 mac address mapping

Decimal IP:: 227 129 16 45Destination MAC in Hex:: 0100 5e 1000 0001 10 30

The destination mac address becomes: Destination MAC in Hex:: 0100 5e 0000 0001 10 30 01005e 01 10 30

This bit flips to 0 then

IP Multicast-to-MAC AddressingOverlap of Multicast MAC AddressesIGMPv2IGMP

How hosts tell routers about group membershipRouters solicit group membership from directly connected hostsRFC 1112 specifies first version of IGMPRFC 2236 specifies current version of IGMPIGMP v3 enhancementsSupports on UNIX system, PCs , and MACSIGMPv2

RFC 2236Membership QueriesQuerier sends IGMP query messages to 224.0.0.1 with ttl = 1Query interval 60 secondsdead interval 180-seconds

Membership ReportsIGMP report sent by one host Suppresses sending by othersRestrict to one report per group per LANUnsolicited reports sent by host, when it first joins the group

IGMPv2

Group-specific queryRouter sends group-specific queries to make sure there are no members present before stopping to forward data for the group for that subnet .

Maximum Response Timer set to 1-second when sending Group-specific queries.

Leave Group messageHost sends leave message if it leaves the group and is the last member (reduces leave latency in comparison to v1)IGMPv2

Querier election mechanismOn Multi-access networks , an IGMP Querier router is elected based on lowest IP address.Only the Querier router sends Queries.

Query-Interval Response TimeGeneral Queries specify max. response time which inform hosts of the maximum time within which a host must respond to General Query.(Improves burstiness of the responses.)Backward compatible with IGMPv1

Udp always carries multicast data , protocol nos for udp is 17 , for igmp it is 2

Membership report or Join

Joining member sendsreport to 224.1.1.2 Immediately upon Joining (same as IGMPv1)IGMP State in Router1R1#sh ip igmp groupsIGMP Connected Group MembershipGroup Address Interface Uptime Expires Last Reporter Group Accounted226.1.1.1 FastEthernet0/0 00:16:56 00:02:31 1.1.1.10224.1.1.2 FastEthernet0/0 00:36:23 00:02:38 1.1.1.10

This is all multicast host address : 224.0.0.1

224.1.1.2

Report #1 Router sends periodic queries#2 One member per group per subnet reports

#3 Other members suppresses those messages

Initially all routers send out a queryRouter w/Lowest IP address "elected" querier

Other routers become "Non-Queriers"IGMP QuerierIGMP Non-QuerierIGMPv2 Querier ElectionDetermining which router is the IGMP Querier R1#sh ip igmp interface fa0/0FastEthernet0/0 is up, line protocol is up Internet address is 1.1.1.1/24 IGMP is enabled on interface Current IGMP host version is 2 Current IGMP router version is 2 IGMP query interval is 60 seconds IGMP querier timeout is 120 seconds IGMP max query response time is 10 seconds Last member query count is 2 Last member query response interval is 1000 ms Inbound IGMP access group is not set IGMP activity: 3 joins, 0 leaves Multicast routing is enabled on interface Multicast TTL threshold is 0 Multicast designated router (DR) is 1.1.1.2 IGMP querying router is 1.1.1.1 (this system) Multicast groups joined by this system (number of users): 224.0.1.40(1)Leaving a group:Host leaves group; sends Leave message224.1.1.1 -> 224.0.0.2- Router sends group specific query (with query response intervalset to 1-second)- A remaining member host sends report (wihtin time set by "query response interval")- Last host leaves; send leave message - Router sends Group specific query- No Report is received- Group times out after 3-seconds (default)