Dell Force10 S55T S55 Configuration Guide FTOS 8.3.5.3 - Page 278
Adjusting Timers, Adjusting Query and Response Timers, Adjusting the IGMP Querier Timeout Value
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www.dell.com | support.dell.com Figure 14-8. Viewing Static and Learned IGMP Groups Force10(conf-if-gi-1/0)#do sho ip igmp groups Total Number of Groups: 2 IGMP Connected Group Membership Group Address Interface Uptime 224.1.1.1 GigabitEthernet 1/0 00:00:03 224.1.2.1 GigabitEthernet 1/0 00:56:55 Expires Never 00:01:22 Last Reporter CLI 1.1.1.2 Adjusting Timers View the current value of all IGMP timers using the command show ip igmp interface from EXEC Privilege mode, as shown in Figure 14-6. Adjusting Query and Response Timers The querier periodically sends a general query to discover which multicast groups are active. A group must have at least one host to be active. When a host receives a query, it does not respond immediately, but rather starts a delay timer. The delay time is set to a random value between 0 and the Maximum Response Time. The host sends a response when the timer expires; in version 2, if another host responds before the timer expires, the timer is nullified, and no response is sent. The Maximum Response Time is the amount of time that the querier waits for a response to a query before taking further action. The querier advertises this value in the query (see Figure 14-1). Lowering this value decreases leave latency but increases response burstiness since all host membership reports must be sent before the Maximum Response Time expires. Inversely, increasing this value decreases burstiness at the expense of leave latency. • Adjust the period between queries using the command ip igmp query-interval from INTERFACE mode. • Adjust the Maximum Response Time using the command ip igmp query-max-resp-time from INTERFACE mode. When the querier receives a leave message from a host, it sends a group-specific query to the subnet. If no response is received, it sends another. The amount of time that the querier waits to receive a response to the initial query before sending a second one is the Last Member Query Interval (LMQI). The switch waits one LMQI after the second query before removing the group from the state table. • Adjust the Last Member Query Interval using the command ip igmp last-member-query-interval from INTERFACE mode. Adjusting the IGMP Querier Timeout Value If there is more than one multicast router on a subnet, only one is elected to be the querier, which is the router that sends queries to the subnet. 1. Routers send queries to the all multicast systems address, 224.0.0.1. Initially, all routers send queries. 278 | Internet Group Management Protocol
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