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98 CHAPTER 5: IP ROUTING PROTOCOL OPERATION
Configuring OSPF Route Filtering
Perform the following configuration in OSPF view.
By default, OSPF does not filter the imported and distributed routing information.
For a detailed description, see “IP Routing Policy”.
Configuring Filling the MTU Field When an Interface Transmits DD Packets
OSPF routers use the DD (Database Description) packets to describe their own
LSDs when synchronizing the databases.
By default, the MTU field in DD packets is 0. You can manually specify an interface
to fill in the MTU field in a DD packet when it transmits the packet. The MTU
should be set to the real MTU on the interface.
Perform the following configuration in VLAN interface view.
By default, the interface does not fill in the MTU field when transmitting DD
packets, and the MTU in the DD packets is 0.
Disabling the Interface to Send OSPF Packets
Use the silent-interface command to prevent the interface from transmitting
OSPF packets.
Perform the following configuration in OSPF view.
By default, all the interfaces are allowed to transmit and receive OSPF packets.
After an OSPF interface is set to silent status, the interface can still advertise its
direct route. However, the OSPF calling packets of the interface are blocked, and
Table 47 Enabling OSPF to Filter the Imported Routes
Operation Command
Enable OSPF filtering of the imported global
routing information
filter-policy { acl-number | ip-prefix
ip-prefix-name | gateway prefix-list- name }
import
Disable filtering of the imported global routing
information
undo filter-policy { acl-number | ip-prefix
ip-prefix-name | gateway prefix- list-name }
import
Table 48 Configuring Filling MTU Field When an Interface Transmits DD Packets
Operation Command
Enable an interface to fill in the MTU field
when transmitting DD packets
ospf mtu-enable
Disable the interface to fill MTU when
transmitting DD packets
undo ospf mtu-enable
Table 49 Disabling the Interface to Send OSPF Packets
Operation Command
Prevent the interface from sending OSPF
packets
silent-interface silent-interface-type
silent-interface-number
Allow the interface to send OSPF packets undo silent-interface silent-interface-type
silent-interface-number