In OSPF, an interface can be configured to act as a connection between a router and one of its attached networks. An interface includes state information that was obtained from underlying lower level protocols and from the routing protocol. An interface to a network is associated with a single IP address and mask. If the address is merely changed, then the OSPF configuration is preserved.
The passive command enables the passive property to and from the OSPF interface where passive interfaces are advertised as OSPF interfaces but do not run the OSPF protocol. By default, only interface addresses that are configured for OSPF are advertised as OSPF interfaces. The passive parameter allows an interface to be advertised as an OSPF interface without running the OSPF protocol. When enabled, the interface will ignore ingress OSPF protocol packets and not transmit any OSPF protocol packets.
An interface can be part of more than one area, as specified in RFC 5185. To do this, add the keyword secondary when creating the interface.
Use the following syntax to configure an OSPF interface.
ospf ospf-instance
area area-id
interface ip-int-name
advertise-subnet
authentication-key [authentication-key|hash-key] [hash|hash2]
authentication-type [password|message-digest]
dead-interval seconds
hello-interval seconds
interface-type {broadcast|point-to-point}
message-digest-key key-id md5 [key|hash-key][hash|hash2]
metric metric
mtu bytes
passive
priority number
retransmit-interval seconds
no shutdown
transit-delay seconds
The following is a sample interface configuration output.
A:ALA-49>config>router>ospf# info
----------------------------------------------
asbr
overload
overload-on-boot timeout 60
traffic-engineering
export "OSPF-Export"
graceful-restart
helper-disable
exit
area 0.0.0.0
virtual-link 1.2.3.4 transit-area 1.2.3.4
hello-interval 9
dead-interval 40
exit
interface "system"
exit
exit
area 0.0.0.20
stub
exit
interface "to-103"
exit
exit
area 0.0.0.25
nssa
exit
exit
area 1.2.3.4
exit
area 4.3.2.1
interface "SR1-3"
exit
exit
area 4.3.2.1
interface "SR1-3" secondary
exit
exit
----------------------------------------------
A:ALA-49>config>router>ospf# area 0.0.0.20