3Com 10014299 manual Specify Hello Intervall, Specify Dead Interval

430CHAPTER 29: CONFIGURING OSPF

Specifying the Hello The Hello packet is periodically sent to the neighboring router to find and maintain Interval OSPF neighbor relationship, and to elect the DR and BDR in the NBMA and

broadcast networks. When one router is started, it only sends hello packets to the neighbors whose precedences are larger than 0, that is, the routers can possibly be elected as DR or BDR. You can configure the interval for sending hello packets. If the interval is too short, the network change can be easily found but the network load will be greatly increased. An appropriate value must be selected for the specific network conditions.

On NBMA and point-to-multipoint networks, the poll-intervalattribute should be configured to specify the period of sending polling hello packet before this interface sets up a neighbor relationdship with the adjacent routers.

The poll-intervalattribute must be at least 3 times the value for hello-timer.

Perform the following configurations in interface view.

Table 494 Specify Hello Intervall

Operation	Command
Set the time interval for the interface to	ospf timer hello seconds
send hello packets
Return to the default hello interval time	undo ospf timer	hello
Specify the length of poll-interval on	ospf timer poll	seconds
NBMA and point-to-multipoint network
type
Return to the default poll interval time	undo ospf timer	poll

By default, the hello-timer on the p2p interface is 10 seconds and the hello timer on the p2mp amd nbma interfaces on the same network segment must be identical.

Specifying the Dead The expiration time of a neighboring router means that if a hello packet of the Interval neighbor router (peer) is not received within a certain period, the neighbor router

is invalid. You can specify the dead-timer, the period where the peer route fails. The value of the dead-timer must be at least 4 times the value of the hello-timer.

Perform the following configurations in interface view.

Table 495 Specify Dead Interval

Operation	Command
Specify the expiration duration of the	ospf timer dead	seconds
OSPF neighbor
Return to the default value of dead	undo ospf timer	dead
interval

By default, the dead-timer on the p2p interface is 40 seconds and on p2mp and nbma interface the dead-timer is 120 seconds, ranging from 1 to 65535 seconds.

Note that:

■The dead-timer of the router on the same network segment must be the same.

■When you modify the network type, the hello-timer and dead-timer are both restored to their default values.