3com S7906E 설치 설명서

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With the hello message filter configured, if hello messages of an existing PIM neighbor fail to pass the 

filter, the PIM neighbor will be removed automatically when it times out. 

 

No matter in a PIM-DM domain or a PIM-SM domain, the hello messages sent among routers contain 

many configurable options, including:  

z 

DR_Priority (for PIM-SM only): priority for DR election. The device with the highest priority wins the 

DR election. You can configure this parameter on all the routers in a multi-access network directly 

connected to multicast sources or receivers. 

z 

Holdtime: the timeout time of PIM neighbor reachability state. When this timer times out, if the 

router has received no hello message from a neighbor, it assumes that this neighbor has expired or 

become unreachable.  

z 

LAN_Prune_Delay: the delay of prune messages on a multi-access network. This option consists 

of LAN-delay (namely, prune message delay), override-interval, and neighbor tracking flag. If the 

LAN-delay or override-interval values of different PIM routers on a multi-access subnet are 

different, the largest value will take effect. If you want to enable neighbor tracking, the neighbor 

tracking feature should be enabled on all PIM routers on a multi-access subnet. 

The LAN-delay setting will cause the upstream routers to delay processing received prune messages.  

The override-interval sets the length of time a downstream router is allowed to wait before sending a 

prune override message. When a router receives a prune message from a downstream router, it does 

not perform the prune action immediately; instead, it maintains the current forwarding state for a period 

of LAN-delay plus override-interval. If the downstream router needs to continue receiving multicast data, 

it must send a prune override message within the prune override interval; otherwise, the upstream route 

will perform the prune action when the period of LAN-delay plus override-interval time out.  

A hello message sent from a PIM router contains a generation ID option. The generation ID is a random 

value for the interface on which the hello message is sent. Normally, the generation ID of a PIM router 

does not change unless the status of the router changes (for example, when PIM is just enabled on the 

interface or the device is restarted). When the router starts or restarts sending hello messages, it 

generates a new generation ID. If a PIM router finds that the generation ID in a hello message from the 

upstream router has changed, it assumes that the status of the upstream neighbor is lost or the 

upstream neighbor has changed. In this case, it triggers a join message for state update.  

If you disable join suppression (namely, enable neighbor tracking), the join suppression feature should 

be disabled on all PIM routers on a multi-access subnet; otherwise, the upstream router will fail to 

explicitly track which downstream routers are joined to it.  

Follow these steps to configure hello options globally:  

To do... 

Use the command... 

Remarks 

Enter system view 

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