3Com 3032 Configuration Manual page 434

430 C 29: C
HAPTER ONFIGURING
Specifying the Hello
Interval
Specifying the Dead
Interval
OSPF
The Hello packet is periodically sent to the neighboring router to find and maintain
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-interval attribute 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-interval attribute must be at least 3 times the value for hello-timer.
Perform the following configurations in interface view.
Table 494 Specify Hello Intervall
Operation
Set the time interval for the interface to
send hello packets
Return to the default hello interval time
Specify the length of poll-interval on
NBMA and point-to-multipoint network
type
Return to the default poll interval time
By default, the hello-timer on the
on the amd
p2mp nbma
identical.
The expiration time of a neighboring router means that if a hello packet of the
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
Specify the expiration duration of the
OSPF neighbor
Return to the default value of dead
interval
By default, the dead-timer on the
interface the dead-timer is 120 seconds, ranging from 1 to 65535 seconds.
nbma
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.
Command
ospf timer hello seconds
undo ospf timer hello
ospf timer poll seconds
undo ospf timer poll
interface is 10 seconds and the hello timer
p2p
interfaces on the same network segment must be
Command
ospf timer dead seconds
undo ospf timer dead
interface is 40 seconds and on
p2p
and
p2mp