ospf timer hello

Function

The ospf timer hello command sets the interval at which Hello packets are sent on an interface.

The undo ospf timer hello command restores the default value.

By default, for P2P and broadcast interfaces, the interval is 10 seconds, for P2MP and NBMA interfaces, the interval is 30 seconds.

Format

ospf timer hello interval [ conservative ]

undo ospf timer hello

Parameters

Parameter	Description	Value
interval	Specifies the interval at which Hello packets are sent on an interface.	The value is an integer ranging from 1 to 65535, in seconds. Setting hello interval to be longer than 2s is recommended.
conservative	Indicates the conservative mode of the dead timer. If the conservative mode is configured, the value configured for the dead timer using the ospf timer dead command takes effect even when the value is less than 10s.	-

Parameter

Description

Value

interval

Specifies the interval at which Hello packets are sent on an interface.

The value is an integer ranging from 1 to 65535, in seconds.

Setting hello interval to be longer than 2s is recommended.

conservative

Indicates the conservative mode of the dead timer. If the conservative mode is configured, the value configured for the dead timer using the ospf timer dead command takes effect even when the value is less than 10s.

Views

100GE interface view, 10GE interface view, 25GE sub-interface view, 25GE interface view, 400GE interface view, 40GE interface view, 50GE sub-interface view, 50GE interface view, Eth-Trunk interface view, FlexE interface view, GE optical interface view, GE electrical interface view, GMPLS-UNI interface view, Global VE sub-interface view, Tunnel interface view, VBDIF interface view, VE sub-interface view, VLANIF interface view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
ospf	write

Usage Guidelines

Usage Scenario

Hello packets are periodically exchanged by OSPF interfaces to establish and maintain neighbor relationships. A Hello packet contains information about timers, DRs, BDRs, and known neighbors.

The smaller the interval value, the faster a network topology change can be detected, and the larger the route cost. Ensure that the parameters of this interface and the adjacent routers are consistent.

To speed up OSPF convergence in the case of a link failure, configuring BFD For OSPF is recommended. If the remote end does not support BFD for OSPF or you do not want to configure BFD for OSPF, specify conservative when you run the ospf timer hello command. If the conservative mode is configured, the value configured for the dead timer using the ospf timer dead command takes effect even when the value is less than 10s; if the value configured for the dead timer is greater than 10s, services may be affected.

Precautions

The ospf timer hello command cannot be run on a null interface.

If the configured interval (X) for sending Hello packets is less than 10s, the actual interval (Y) for sending Hello packets is calculated using the following formula:
Y = X/2 + X%2, where X/2 refers to the rounded-off value of X divided by 2, and X%2 refers to X mod 2. For example, if X equals 5, then X/2 equals 2, and X%2 equals 1.
If the interval for sending Hello packets is set and the ospf timer dead command is not run, the dead interval for OSPF neighbors is four times the interval for sending Hello packets. Therefore, if the interval for sending Hello packets is less than or equal to 2s, the dead interval for OSPF neighbors is less than 10s. In this case, if no Hello packets are received within the dead interval, the neighbor relationships are disconnected. To prevent neighbor relationship flapping and improve network reliability, the system automatically sets the dead interval for OSPF neighbors to 10s if the actual dead interval is less than 10s. However, if the conservative mode is enabled for the dead interval for OSPF neighbors, the dead interval that is four times the interval for sending Hello packets is still used to check whether OSPF neighbors are valid.

Example

# Set the interval at which Hello packets are sent on GigabitEthernet 0/1/0 to 20 seconds.

<HUAWEI> system-view
[~HUAWEI] interface GigabitEthernet0/1/0
[~HUAWEI-GigabitEthernet0/1/0] ospf timer hello 20