Note: You must perform Lab 0 for loading the initial configurations before starting this lab.
● Configure OSPF in area 0 between R6, R7 and R9.
✓ Use a OSPF network type of point-to-point.
● Advertise Loopback0 prefixes in area 0.
Configurations
R6:
!
enable
configure terminal
!
interface GigabitEthernet0/1
ip ospf 1 area 0
ip ospf network point-to-point
!
interface Loopback0
ip ospf 1 area 0
!
end
!
write
!
R7:
!
enable
configure terminal
!
interface GigabitEthernet0/1
ip ospf 1 area 0
ip ospf network point-to-point
!
interface GigabitEthernet0/2
ip ospf 1 area 0
ip ospf network point-to-point
!
interface Loopback0
ip ospf 1 area 0
!
end
!
write
!
R9:
!
enable
configure terminal
!
interface GigabitEthernet0/0
ip ospf 1 area 0
ip ospf network point-to-point
!
interface Loopback0
ip ospf 1 area 0
!
end
!
write
!
Verifications
The Default OSPF network on Ethernet interfaces is Broadcast. OSPF network point-to-point is the default option for point-to-point interfaces such as HDLC, PPP, or point-to-point GRE tunnels. It uses multicast hellos, does not use the DR/BDR election, and only supports the adjacency of exactly two neighbors on a segment.
No special design considerations need be accounted for with point-to-point OSPF interfaces. The default OSPF network type (before applying commad ip ospf network point-to-point on both R6 Gi0/1 and R7 Gi0/1) can be verified by using the show ip ospf interface command:
R6#show ip ospf interface gigabitEthernet 0/1
GigabitEthernet0/1 is up, line protocol is up
Internet Address 177.1.67.6/24, Area 0, Attached via Interface Enable
Process ID 1, Router ID 170.1.6.6, Network Type BROADCAST, Cost: 1
Topology-MTID Cost Disabled Shutdown Topology Name
0 1 no no Base
Enabled by interface config, including secondary ip addresses
Interface PID Area IP Address/Mask Cost State Nbrs F/C
Lo0 1 0 170.1.6.6/32 1 LOOP 0/0
Gi0/1 1 0 177.1.67.6/24 1 P2P 1/1
The null output after the slash in the State column of the show ip ospf neighbor output indicates that no DR or BDR is elected for network type point-to-point:
Neighbor priority is 0, State is FULL, 6 state changes
DR is 0.0.0.0 BDR is 0.0.0.0
Options is 0x12 in Hello (E-bit, L-bit)
Options is 0x52 in DBD (E-bit, L-bit, O-bit)
LLS Options is 0x1 (LR)
Dead timer due in 00:00:38
Neighbor is up for 00:20:09
Index 1/2/2, retransmission queue length 0, number of retransmission 1
First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0)
Last retransmission scan length is 1, maximum is 1
Last retransmission scan time is 0 msec, maximum is 0 msec
Neighbor 170.1.6.6, interface address 177.1.67.6
In the area 0 via interface GigabitEthernet0/1
Neighbor priority is 0, State is FULL, 6 state changes
DR is 0.0.0.0 BDR is 0.0.0.0
Options is 0x12 in Hello (E-bit, L-bit)
Options is 0x52 in DBD (E-bit, L-bit, O-bit)
LLS Options is 0x1 (LR)
Dead timer due in 00:00:37
Neighbor is up for 00:01:15
Index 1/1/1, retransmission queue length 0, number of retransmission 0
First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0)
Last retransmission scan length is 0, maximum is 0
Last retransmission scan time is 0 msec, maximum is 0 msec
The lack of DR/BDR can also be observer due to missing of Type2 LSA in the OSPF database:
R7#show ip ospf database
OSPF Router with ID (177.1.7.7) (Process ID 1)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count
170.1.6.6 170.1.6.6 95 0x80000008 0x009B95 3
177.1.7.7 177.1.7.7 94 0x80000008 0x002C09 5
177.1.9.9 177.1.9.9 1230 0x80000001 0x00EA12 3
Note that for point-to-point OSPF network types, the Type1 LSA contains both the network segment but also information about the neighbor OSPF router, which isrequired for a complete database view. For example R6 LSA Type1 has information about its neighbor R7 on the point-to-point link
R6#show ip ospf database router self-originate
OSPF Router with ID (170.1.6.6) (Process ID 1)
Router Link States (Area 0)
LS age: 132
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 170.1.6.6
Advertising Router: 170.1.6.6
LS Seq Number: 80000008
Checksum: 0x9B95
Length: 60
Number of Links: 3
Link connected to: a Stub Network
(Link ID) Network/subnet number: 170.1.6.6
(Link Data) Network Mask: 255.255.255.255
Number of MTID metrics: 0
TOS 0 Metrics: 1
Link connected to: another Router (point-to-point)
