Configuring OSPF Default Route Propagation
Advertising a default route into OSPF can be done multiple ways, through the use of redistribution or default information originate. This lab will discuss and demonstrate the configuration and verification of OSPF default route propagation.
Real World Application & Core Knowledge
Configuring OSPF to advertise a default route through out the OSPF domain is very similar configuring the default route propagation in the Routing Information Protocol (RIP) found in Lab 7-7 – Configuring Rip Default Information Originate except there are two differences.
In RIP you use the default-information originate command in RIP router configuration mode and this will advertise a default route through out the RIP domain. However if you issue this command in OSPF router configuration mode this will advertise a default route from the router as a type 5 LSA in a normal area (Non-Backbone/Non Stub Area). This command will not advertise a default route unless a static default route exist on the router you’ve issued this command on.
In order to advertise a default route through out area 0 such as a route to an ISP you can use the default-information originate always in OSPF router configuration mode which will advertises a type 3 0.0.0.0/0 LSA to the entire network or you can redistribute a static default route into the OSPF routing process which will be discussed in Section 10.
In this lab you will configure R1 to advertise a default route to all routers in the OSPF autonomous system.
Familiarize yourself with the following new command(s);
| Command | Description |
| default-information originate | This command is executed in OSPF router configuration mode to advertise the default route as a type 3 Summary LSA to 0.0.0.0/0 only if a default route already exist in the routing table. |
| default-information originate always | This command is executed in OSPF router configuration mode to always advertise the default route as a type 3 Summary LSA to 0.0.0.0/0. |
The following logical topology shown below is used in labs found through out Section 9 – Configuring OSPF;
Lab Prerequisites
- If you are using GNS3 than load the Stub Area Networking GNS3 topology than start devices; R1, R2, R3, R4, R5 and SW1.
- Establish a console session with devices R1, R2, R3, R4, R5 and SW1 than load the initial configurations provided below by copying the config from the textbox and pasting it into the respected routers console.
!##################################################
!# Free CCNA Workbook Lab 9-15 R1 Initial Config #
!##################################################
!
enable
configure terminal
!
hostname R1
no ip domain-lookup
!
interface Loopback0
description ### SIMULATED NETWORK ###
ip address 10.90.10.1 255.255.255.0
ip ospf 1 area 1
!
interface Serial0/0
description ### PHYSICAL FRAME RELAY INTERFACE ###
ip address 10.90.245.1 255.255.255.248
ip ospf 1 area 0
encapsulation frame-relay
serial restart-delay 0
frame-relay map ip 10.90.245.5 125 broadcast
frame-relay map ip 10.90.245.4 124 broadcast
frame-relay map ip 10.90.245.2 122 broadcast
no frame-relay inverse-arp
no shut
exit
!
router ospf 1
router-id 1.1.1.1
log-adjacency-changes
auto-cost reference-bandwidth 100000
maximum-paths 1
neighbor 10.90.245.2
neighbor 10.90.245.4
neighbor 10.90.245.5
!
line con 0
logging sync
no exec-timeout
!
end
!##################################################
!# Free CCNA Workbook Lab 9-15 R2 Initial Config #
!##################################################
!
enable
configure terminal
!
hostname R2
no ip domain-lookup
!
interface Loopback0
description ### SIMULATED NETWORK ###
ip address 10.90.20.1 255.255.255.0
ip ospf 1 area 2
!
interface Serial0/0
description ### PHYSICAL FRAME RELAY INTERFACE ###
ip address 10.90.245.2 255.255.255.248
encapsulation frame-relay
ip ospf priority 0
ip ospf 1 area 0
serial restart-delay 0
no frame-relay inverse-arp
frame map ip 10.90.245.1 221 broadcast
frame map ip 10.90.245.4 221
frame map ip 10.90.245.5 221
no shut
!
interface Serial0/2
POINT-TO-POINT LINK TO R3
ip address 10.90.23.1 255.255.255.252
ip ospf 1 area 3
ip ospf hello-interval 1
encapsulation ppp
serial restart-delay 0
no shut
exit
!
router ospf 1
router-id 2.2.2.2
auto-cost reference-bandwidth 100000
log-adjacency-changes
area 3 stub no-summary
!
line con 0
logging sync
no exec-timeout
!
end
!##################################################
!# Free CCNA Workbook Lab 9-15 R3 Initial Config #
!##################################################
!
enable
configure terminal
!
hostname R3
no ip domain-lookup
!
interface Loopback0
description ### SIMULATED NETWORK ###
ip address 10.90.30.1 255.255.255.0
ip ospf 1 area 3
!
interface Serial0/1
description ### POINT-TO-POINT LINK TO R2 ###
ip address 10.90.23.2 255.255.255.252
ip ospf 1 area 3
ip ospf hello-interval 1
encapsulation ppp
no shut
exit
!
router ospf 1
router-id 3.3.3.3
log-adjacency-changes
auto-cost reference-bandwidth 100000
area 3 stub
!
line con 0
logging sync
no exec-timeout
!
end
!##################################################
!# Free CCNA Workbook Lab 9-15 R4 Initial Config #
!##################################################
!
enable
configure terminal
!
hostname R4
no ip domain-lookup
!
interface Loopback0
description ### SIMULATED NETWORK ###
ip address 10.90.40.1 255.255.255.0
ip ospf 1 area 4
!
interface Loopback4
description ### SIMULATED NETWORK ###
ip address 10.44.4.1 255.255.255.0
ip ospf 1 area 44
!
interface Loopback5
description ### SIMULATED NETWORK ###
ip address 10.44.5.1 255.255.255.0
ip ospf 1 area 44
!
interface Loopback6
description ### SIMULATED NETWORK ###
ip address 10.44.6.1 255.255.255.0
ip ospf 1 area 44
!
interface Loopback7
description ### SIMULATED NETWORK ###
ip address 10.44.7.1 255.255.255.0
ip ospf 1 area 44
!
interface FastEthernet0/0
description ### REAL NETWORK ###
ip address 10.90.145.1 255.255.255.0
ip ospf 1 area 45
no shut
!
interface Serial0/0
description ### PHYSICAL FRAME RELAY INTERFACE ###
ip address 10.90.245.4 255.255.255.248
encapsulation frame-relay
ip ospf priority 0
ip ospf 1 area 0
serial restart-delay 0
no frame-relay inverse-arp
frame map ip 10.90.245.1 421 broadcast
frame map ip 10.90.245.2 421
frame map ip 10.90.245.5 421
no shut
!
interface Serial0/1
description ### POINT-TO-POINT LINK TO R5 ###
ip address 10.90.45.1 255.255.255.252
ip ospf 1 area 45
encapsulation ppp
serial restart-delay 0
no shut
exit
!
router ospf 1
router-id 4.4.4.4
auto-cost reference-bandwidth 100000
log-adjacency-changes
passive-interface fastethernet0/0
!
line con 0
logging sync
no exec-timeout
!
end
!##################################################
!# Free CCNA Workbook Lab 9-15 R5 Initial Config #
!##################################################
!
enable
configure terminal
!
hostname R5
no ip domain-lookup
!
interface Loopback0
description ### SIMULATED NETWORK ###
ip address 10.90.50.1 255.255.255.0
ip ospf 1 area 5
!
interface FastEthernet0/0
description ### REAL NETWORK ###
ip address 10.90.145.2 255.255.255.0
ip ospf cost 65535
ip ospf 1 area 45
no shut
!
interface Serial0/0
description ### PHYSICAL FRAME RELAY INTERFACE ###
ip address 10.90.245.5 255.255.255.248
encapsulation frame-relay
ip ospf priority 0
ip ospf 1 area 0
serial restart-delay 0
no frame-relay inverse-arp
frame map ip 10.90.245.1 521 broadcast
frame map ip 10.90.245.2 521
frame map ip 10.90.245.4 521
no shut
!
interface Serial0/1
description ### POINT-TO-POINT LINK TO R4 ###
ip address 10.90.45.2 255.255.255.252
ip ospf 1 area 45
encapsulation ppp
serial restart-delay 0
no shut
exit
!
router ospf 1
router-id 5.5.5.5
log-adjacency-changes
auto-cost reference-bandwidth 100000
passive-interface fastethernet0/0
!
line con 0
logging sync
no exec-timeout
!
end
!##################################################
!# Free CCNA Workbook Lab 9-X SW1 Initial Config #
!##################################################
!
enable
configure terminal
!
hostname SW1
no ip domain-lookup
!
line con 0
logging sync
no exec-timeout
!
end
Lab Objectives
- Configure R1 to always originate a default route through out the entire OSPF autonomous system.
- Verify that the default route is being propagated correctly by viewing the routing table on R4.
Lab Instruction
Objective 1. – Configure R1 to always originate a default route through out the entire OSPF autonomous system.
R1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#router ospf 1
R1(config-router)#default-information originate always
R1(config-router)#end
R1#
<br>
Objective 2. – Verify that the default route is being propagated correctly by viewing the routing table on R4.
R4#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
* - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is 10.90.245.1 to network 0.0.0.0
10.0.0.0/8 is variably subnetted, 15 subnets, 5 masks
O IA 10.90.50.1/32 [110/64767] via 10.90.245.5, 00:54:52, Serial0/0
C 10.90.40.0/24 is directly connected, Loopback0
O IA 10.90.23.0/30 [110/129532] via 10.90.245.2, 00:54:52, Serial0/0
C 10.44.6.0/24 is directly connected, Loopback6
C 10.44.7.0/24 is directly connected, Loopback7
O IA 10.90.30.1/32 [110/129533] via 10.90.245.2, 00:26:12, Serial0/0
C 10.44.4.0/24 is directly connected, Loopback4
O 10.44.4.0/22 is a summary, 00:54:52, Null0
C 10.44.5.0/24 is directly connected, Loopback5
C 10.90.45.2/32 is directly connected, Serial0/1
C 10.90.145.0/24 is directly connected, FastEthernet0/0
C 10.90.45.0/30 is directly connected, Serial0/1
O IA 10.90.20.1/32 [110/64767] via 10.90.245.2, 00:54:53, Serial0/0
O IA 10.90.10.1/32 [110/64767] via 10.90.245.1, 00:54:53, Serial0/0
C 10.90.245.0/29 is directly connected, Serial0/0
O*E2 0.0.0.0/0 [110/1] via 10.90.245.1, 00:00:17, Serial0/0
R4#
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