The ospf mtu-enable command enables an 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 command restores the default settings.
By default, an 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.
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 command to configure an 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.
Precautions
OSPF does not support the configuration on a null interface.
After the command is configured, the system automatically restarts the OSPF process.
# Set Vlanif100 to fill in the MTU field when sending DD packets.
<HUAWEI> system-view
[HUAWEI] interface vlanif 100
[HUAWEI-Vlanif100] ospf mtu-enable
# Set GigabitEthernet0/0/1 to fill in the MTU field when sending DD packets.
<HUAWEI> system-view [HUAWEI] interface gigabitethernet 0/0/1 [HUAWEI-GigabitEthernet0/0/1] undo portswitch [HUAWEI-GigabitEthernet0/0/1] ospf mtu-enable