ospf mtu-enable multi-area

Function

The ospf mtu-enable multi-area command enables a multi-area adjacency interface to add its actual MTU in DD packets to be sent and check whether the MTU in a received DD packet is greater than the local MTU.

The undo ospf mtu-enable multi-area command restores the default configuration.

By default, a multi-area adjacency interface adds the MTU 0 (not the actual MTU) in DD packets to be sent and does not check the MTUs in received DD packets.

Format

ospf mtu-enable multi-area { area-id | area-id }

undo ospf mtu-enable multi-area { area-id | area-id }

Parameters

Parameter	Description	Value
area-id	Specifies the ID of an OSPF area.	The value can be a decimal integer ranging from 0 to 4294967295 or in the format of an IP address.

Parameter

Description

Value

area-id

Specifies the ID of an OSPF area.

The value can be a decimal integer ranging from 0 to 4294967295 or in the format of an IP address.

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

To improve compatibility with a non-Huawei device, an OSPF-enabled Huawei device adds the MTU 0 in DD packets to be sent and does not check the MTUs in received DD packets, allowing an OSPF neighbor relationship to be set up even if the two ends have different MTU settings.

However, under the default configuration, the non-Huawei device may discard an OSPF packet received from the Huawei device if the packet's actual MTU is greater than the MTU of the non-Huawei device. If the discarded packet is an LSU, an OSPF neighbor relationship can still be set up, but the route carried in the LSU fails to be learned, causing service interruptions.

To resolve this issue, run the ospf mtu-enable multi-area command to configure a multi-area adjacency interface to add the actual MTU in DD packets to be sent and check whether the MTU in a received DD packet is greater than the local MTU. If the interface MTU settings of the local and remote ends are different, an OSPF neighbor relationship cannot enter the Full state. In this manner, MTU inconsistency can then be identified in time.

Prerequisites

The ospf enable multi-area command has been run.

Precautions

The ospf mtu-enable multi-area command does not apply to null interfaces.

After the ospf mtu-enable multi-area command is run, the OSPF neighbor relationship is reestablished.

Example

# Enable multi-area adjacency interface to add its MTU to the DD packets to be sent.

<HUAWEI> system-view
[~HUAWEI] ospf 1
[*HUAWEI-ospf-1] area 0
[*HUAWEI-ospf-1-area-0.0.0.0] quit
[*HUAWEI-ospf-1] area 1
[*HUAWEI-ospf-1-area-0.0.0.1] quit
[*HUAWEI-ospf-1] quit
[*HUAWEI] interface GigabitEthernet 0/1/0
[*HUAWEI-GigabitEthernet0/1/0] ospf enable 1 area 0
[*HUAWEI-GigabitEthernet0/1/0] ospf enable multi-area 1
[*HUAWEI-GigabitEthernet0/1/0] ospf mtu-enable multi-area 1