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Pic. 1 - Topology Diagram.
In order to use the above topology here are useful links:
GNS3 Topology
OSPF Labs Initial Configuration (Pic. 1)
Task 1
Using the most specific wildcard mask, enable OSPF area 13 between R1 and R3 on their point-to-point (serial0/1) connection. Do not change the default OSPF mode.
Task 2
Using the most specific wildcard mask advertise addresses of both (R1 and R3) Loopback0 interfaces into OSPF. Verify the connection between them.
Save the configuration for the next lab.
Questions
Task 2
Using the most specific wildcard mask advertise addresses of both (R1 and R3) Loopback0 interfaces into OSPF. Verify the connection between them.
Save the configuration for the next lab.
Questions
- What is the default OSPF mode of operation on point-to-point links? How would you verify it?
- What are the hello and dead intervals in OSPF point-to-point mode?
- Is point-to-point OSPF mode Cisco proprietary or RFC standard?
- What are the three ways of advertising networks into OSPF?
- Which command displays the configured routing protocols?
- Which command provides brief output of all OSPF-enabled interfaces?
- What is the order in which OSPF chooses its ID?
Task 1
Using the most specific wildcard mask, enable OSPF area 13 between R1 and R3 on their point-to-point (serial0/1) connection. Do not change the default OSPF mode.
R1 Config:
!
router ospf 1
network 172.16.13.1 0.0.0.0 area 13
!
R3 Config:
!
router ospf 1
network 172.16.13.3 0.0.0.0 area 13
!
Task 2
Using the most specific wildcard mask advertise addresses of both (R1 and R3) Loopback0 interfaces into OSPF. Verify the connection between them.
Save the configuration for the next lab.
R1 Config:
!
router ospf 1
network 10.0.1.1 0.0.0.0 area 13
!
R3 Config:
!
router ospf 1
network 10.0.3.3 0.0.0.0 area 13
!
What You Should See
Pic. 2.
Pic. 3.
Pic.4.
Study Drill
Notice, that the default OSPF mode of operation on point-to-point links is ... creatively enough 'point-to-point'. This is a Cisco proprietary OSPF mode. But what does constitute a point-to-point link (link = interface) in OSPF world?
A serial interface that is running point-to-point protocol (HDLC, PPP) or point-to-point
sub-interface will be 'seen' by OSPF as candidates to run point-to-point mode. This is the easiest and safest, almost idiot-proof type of OSPF.
sub-interface will be 'seen' by OSPF as candidates to run point-to-point mode. This is the easiest and safest, almost idiot-proof type of OSPF.
OSPF point-to-point will use 10 seconds for its 'hello' packets and the dead interval is going is set to 40 second by default (remember, these timers as well as area ID, area type, authentication and MTU size must match for proper OSPF neighbor relationship and LSA exchange).
If you want to see what is the OSPF mode used on an interface type:
show ip ospf interface
You can follow this command by an interface type/number. If you want to get a nice, brief output of all interfaces enabled in OSPF use: 'show ip ospf interface brief' command.
The 'show ip protocols' command will display information of all routing protocols configured on a router.
OSPF protocol builds very accurate database of all links and routers advertising them in the area. In order to do this it assumes that each router in OSPF domain has a unique identifier (router-id). You can check it using a bunch of commands. Here's just a few of them:
show ip ospf interface
show ip protocols
show ip ospf | include ID
