Инструкции По Установке для 3com S7906E

 

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Upon receiving an IGMP leave message, the IGMP querier sends “last member query count” IGMP 

group-specific queries at the “IGMP last member query interval”. IGMP is robust to “robustness variable 

minus 1” packet losses on a network. Therefore, a greater value of the robustness variable makes the 

IGMP querier “more robust”, but results in a longer multicast group timeout time.  

Upon receiving an IGMP query (general query or group-specific query), a host starts a delay timer for 

each multicast group it has joined. This timer is initialized to a random value in the range of 0 to the 

maximum response time, which is derived from the Max Response Time field in the IGMP query. When 

the timer value comes down to 0, the host sends an IGMP report to the corresponding multicast group.  

An appropriate setting of the maximum response time for IGMP queries allows hosts to respond to 

queries quickly and avoids bursts of IGMP traffic on the network caused by reports simultaneously sent 

by a large number of hosts when the corresponding timers expires simultaneously.  

z 

For IGMP general queries, you can configure the maximum response time to fill their Max 

Response time field.  

z 

For IGMP group-specific queries, you can configure the IGMP last member query interval to fill 

their Max Response time field. Namely, for IGMP group-specific queries, the maximum response 

time equals the IGMP last member query interval.  

When multiple multicast routers exist on the same subnet, the IGMP querier is responsible for sending 

IGMP queries. If a non-querier router receives no IGMP query from the querier within the “other querier 

present interval”, it will assume the querier to have expired and a new querier election process is 

launched; otherwise, the non-querier router will reset its “other querier present timer”.  

Follow these steps to configure IGMP query and response parameters globally:  

To do... 

Use the command... 

Remarks  

Enter system view 

— 

Enter public instance IGMP 
view or VPN instance IGMP 
view 

igmp [ vpn-instance 
vpn-instance-name ] 

— 

Configure the startup query 
interval 

startup-query-interval interval

Optional 

For the system default, see 
“Note” below. 

Configure the startup query 
count 

startup-query-count value 

Optional 

For the system default, see 
“Note” below. 

Configure the IGMP query 
interval  

timer query interval 

Optional 

60 seconds by default  

Configure the IGMP querier 
robustness variable 

robust-count robust-value 

Optional 

2 by default 

Configure the maximum 
response time for IGMP 
general queries 

max-response-time interval 

Optional 

10 seconds by default  

Configure the IGMP last 
member query interval  

last-member-query-interval 
interval 

Optional 

1 second by default