Multicast - IGMP timers

Overview

On any LAN segment a router is elected the IGMP querier which is responsible for polling IGMP hosts to see if they still wish to be joined to a group by sending IGMP membership queries to all hosts on a LAN segment. All receivers should respond with an IGMP report containing all joined groups. The IGMP Querier is elected by lowest IP address, unlike the DR which is elected by highest IP address. The IGMP timers are listed below

• ip igmp query-interval == Interval Querier sends host-query messages
•  [time-in-seconds] == max time receivers will wait before before responding to a igmp group membership report query. Should be less the query interval.
• ip igmp last-member-query-interval [time-in-ms] == The interval between leave query messages that are sent when a receive sends a leave message.
• ip igmp last-member-query-count [number] == Maximum number of leave queries sent before remove IGMP state for a given group if no response is heard.
• ip igmp immediate-leave group-list [list] == Multicast groups which will be imediately removed from IGMP forwarding state.
• ip igmp querier-timeout == interval to wait for host-query messages from IGMP querier before attempting re-election

Concepts tested

• Configuring PIM SM
• Configuring IGMP timers
• Verification of configuration

Topology

Lab Tasks

• Configure PIM SM on all paths between R1 and R5
• Configure the following for the designated IGMP queirier on the 120.0.0.0/24 network segment
• IGMP query interval should be 20 seconds
• Time receivers should wait before sending query responses should be 5 seconds
• Querier should wait 500 ms before sending out-of-sequence query for a maximum of 3 times
• IGMP querier failures should be detected in 60 seconds
• Membership leave notifications for the group range 224.0.0.0 /5 should be immediate

GNS3 configuration file, requires IOS v15 for the 7200 router: Link


Solution

R1(config)#ip multicast-routing
R1(config)#int g0/0
R1(config-if)#ip pim sparse-mode

R1(config-if)#exit

R2(config)#ip multicast-routing

R2(config)#int g0/0

R2(config-if)#ip pim sparse-mode

R2(config-if)#exit

R2(config)#

R2(config)#int g1/0

R2(config-if)#ip pim sparse-mode

R2(config-if)#exit

R2(config)#

R3(config)#ip multicast-routing

R3(config)#int g0/0

R3(config-if)#ip pim sparse-mode

R3(config-if)#exit

R3(config)#

R3(config)#int g1/0

R3(config-if)#ip pim sparse-mode

R3(config-if)#exit

R3(config)#

R4(config)#ip multicast-routing

R4(config)#int g0/0

R4(config-if)#ip pim sparse-mode

R4(config-if)#exit

R4(config)#

R4(config)#int g1/0

R4(config-if)#ip pim sparse-mode

R4(config-if)#exit

R4(config)#

R4(config)#int g2/0

R4(config-if)#ip pim sparse-mode

R4(config-if)#exit

R4(config)#

R4(config)#int loopback 0

R4(config-if)#ip pim sparse-mode

R4(config-if)#exit

R4(config)#

R4(config)#ip pim bsr-candidate loopback 0

R4(config)#ip pim rp-candidate loopback 0

R4(config)#

R4(config)#

R5(config)#ip multicast-routing
R5(config)#int g0/0
R5(config-if)#ip pim sparse-mode
R5(config-if)#exit

R5(config)#

R1#sh ip igmp interface g0/0

  Multicast designated router (DR) is 120.0.0.3

  IGMP querying router is 120.0.0.1 (this system)

R1(config)#ip access-list standard LEAVE_GROUP
R1(config-std-nacl)#permit 224.0.0.0 7.255.255.255
R1(config-std-nacl)#
R1(config-std-nacl)#Interface g0/0
R1(config-if)#ip igmp query-interval 20
R1(config-if)#ip igmp query-max-response-time 5

R1(config-if)#ip igmp querier-timeout 60

R1(config-if)#ip igmp last-member-query-interval 500
R1(config-if)#ip igmp last-member-query-count 3
R1(config-if)#ip igmp immediate-leave group-list LEAVE_GROUP

R2(config)#int g0/0

R2(config-if)#ip igmp querier-timeout 60

R2(config-if)#exit

R3(config)#int g0/0

R3(config-if)#ip igmp querier-timeout 60

R3(config-if)#exit

Verification

GigabitEthernet0/0 is up, line protocol is up
  Internet address is 120.0.0.1/24
  IGMP is enabled on interface
  Current IGMP host version is 2
  Current IGMP router version is 2
  IGMP query interval is 20 seconds
  IGMP configured query interval is 20 seconds
  IGMP querier timeout is 60 seconds
  IGMP configured querier timeout is 60 seconds
  IGMP max query response time is 5 seconds
  Last member query count is 3
  Last member query response interval is 500 ms
  Inbound IGMP access group is not set
  IGMP activity: 1 joins, 0 leaves
  Multicast routing is enabled on interface
  Multicast TTL threshold is 0
  Multicast designated router (DR) is 120.0.0.3
  IGMP querying router is 120.0.0.1 (this system)
  Multicast groups joined by this system (number of users):
      224.0.1.40(1)

R2:

R2(config)#int g0/0

R2(config-if)#ip ig

R2(config-if)#ip igmp join

R2(config-if)#ip igmp join-group 224.0.10.1

R2(config-if)#no ip igmp join-group 224.0.10.1

R2(config-if)#

R1:

*Dec  5 03:37:17.229: IGMP(0): Received Leave from 120.0.0.2 (GigabitEthernet0/0) for 224.0.10.1

*Dec  5 03:37:17.233: IGMP(0): Leave group 224.0.10.1 immediately on GigabitEthernet0/0

*Dec  5 03:37:17.237: IGMP(0): Deleting 224.0.10.1 on GigabitEthernet0/0