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OSPF default routing

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By Edgar C Francis Internetworks

 

OSPF Default Route

Configuring OSPF Default route is not a big problem. We have couple of options when we want to OSPF default route. Here is an example

R1(config)#router ospf 1 
R1(config-router)#default-information originate ?
  always       Always advertise default route
  metric       OSPF default metric
  metric-type  OSPF metric type for default routes
  route-map    Route-map reference
  <cr>

We can change numbers of things for example metric or metric type but most of the people forget about the most important thing is the always keyword.  If we add the always command this feature advertises the default route even if we do not have in our routing table. It will look like that route is installed in routing table.  

When we use the default information originate we can advertise a default route in OSPF. But OSPF won’t advertise a default route if we do not already installed in our routing table. 


Topology :

OSPF default routing 


TASK:


  • configure the topology as per the diagram 
  • configure IP addresses as our topology 
  • configure Router 1, 2, 3 and 4 OSPF in area 0
  • make sure router 1, 2, 3, and 4 able to reach router 5 internet route using default route.


R1(config)#Interface fastethernet 0/0
R1(config-if)#Ip address 10.1.1.1   255.0.0.0
R1(config-if)#No shutdown
R1(config-if)#No keepalive
R1(config-if)#Exit

R1(config)#Interface serial 3/0
R1(config-if)#Ip address  1.1.1.1 255.0.0.0
R1(config-if)#No shutdown
R1(config-if)#Exit

R2(config)#Interface fastethernet 0/0
R2(config-if)#Ip address 20.1.1.1   255.0.0.0
R2(config-if)#No shutdown
R2(config-if)#No keepalive
R2(config-if)#Exit

R2(config)#Interface serial 3/0
R2(config-if)#Ip address  1.1.1.2 255.0.0.0
R2(config-if)#No shutdown
R2(config-if)#Exit

R2(config)#Interface serial 3/1
R2(config-if)#Ip address  4.4.4.2 255.0.0.0
R2(config-if)#No shutdown
R2(config-if)#Exit

R2(config)#Interface serial 3/2
R2(config-if)#Ip address  3.3.3.2 255.0.0.0
R2(config-if)#No shutdown
R2(config-if)#Exit

R2(config)#interface serial 3/3
R2(config-if)#ip address 5.5.5.2 255.0.0.0
R2(config-if)#no shutdown
R2(config-if)#exit


R3(config)#Interface fastethernet 0/0
R3(config-if)#Ip address 30.1.1.1   255.0.0.0
R3(config-if)#No shutdown
R3(config-if)#No keepalive
R3(config-if)#Exit

R3(config)#Interface serial 3/2
R3(config-if)#Ip address  3.3.3.1 255.0.0.0
R3(config-if)#No shutdown
R3(config-if)#Exit

R4(config)#Interface fastethernet 0/0
R4(config-if)#Ip address 40.1.1.1   255.0.0.0
R4(config-if)#No shutdown
R4(config-if)#No keepalive
R4(config-if)#Exit

R4(config)#Interface serial 3/1
R4(config-if)#Ip address  4.4.4.1 255.0.0.0
R4(config-if)#No shutdown
R4(config-if)#Exit

R5(config)#Interface fastethernet 0/0
R5(config-if)#Ip address 50.1.1.1   255.0.0.0
R5(config-if)#No shutdown
R5(config-if)#No keepalive
R5(config-if)#Exit

R5(config)#Interface serial 3/3
R5(config-if)#Ip address  5.5.5.1 255.0.0.0
R5(config-if)#No shutdown
R5(config-if)#Exit

R5(config)#Interface loopback  1
R5(config-if)#Ip address 15.0.1.1 255.255.255.0
R5(config-if)#Exit

R5(config)#Interface loopback  2
R5(config-if)#Ip address 15.0.2.1 255.255.255.0
R5(config-if)#Exit

R5(config)#Interface loopback 3
R5(config-if)#Ip address 15.0.3.1 255.255.255.0
R5(config-if)#Exit



R1#show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol
FastEthernet0/0        10.1.1.1        YES manual up                    up
Serial3/0                    1.1.1.1         YES manual up                    up

R2#show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol
FastEthernet0/0        20.1.1.1        YES manual up                    up
Serial3/0                    1.1.1.2         YES manual up                    up
Serial3/1                    4.4.4.2         YES manual up                    up
Serial3/2                    3.3.3.2         YES manual up                    up
Serial3/3                    5.5.5.2         YES manual up                    up



R3#show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol
FastEthernet0/0        30.1.1.1        YES manual up                    up
Serial3/2                    3.3.3.1         YES manual up                    up


R4#show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol
FastEthernet0/0        40.1.1.1        YES manual up                    up
Serial3/1                    4.4.4.1         YES manual up                    up



R5#show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol
FastEthernet0/0        50.1.1.1        YES manual up                    up
Serial3/3                    5.5.5.1         YES manual up                   up
Loopback1              15.0.1.1        YES manual up                    up
Loopback2              15.0.2.1        YES manual up                    up
Loopback3              15.0.3.1        YES manual up                    up


R1(config)#router ospf 1
R1(config-router)#network 10.0.0.0 0.255.255.255 area 0
R1(config-router)#network 1.0.0.0 0.255.255.255 area 0
R1(config-router)#exit


R2(config)#router ospf 1
R2(config-router)#network 1.0.0.0 0.255.255.255 area 0
R2(config-router)#network 3.0.0.0 0.255.255.255 area 0
R2(config-router)#network 4.0.0.0 0.255.255.255 area 0
R2(config-router)#network 20.0.0.0 0.255.255.255 area 0
R2(config-router)#exit

*Dec  4 06:18:03.107: %OSPF-5-ADJCHG: Process 1, Nbr 10.1.1.1 on Serial3/0 from LOADING to FULL, Loading Done

*Dec  4 06:18:57.211: %OSPF-5-ADJCHG: Process 1, Nbr 30.1.1.1 on Serial3/2 from LOADING to FULL, Loading Done

*Dec  4 06:19:45.587: %OSPF-5-ADJCHG: Process 1, Nbr 40.1.1.1 on Serial3/1 from LOADING to FULL, Loading Done


R3(config)#router ospf 1
R3(config-router)#network 3.0.0.0 0.255.255.255 area 0
R3(config-router)#network 3.0.0.0 0.255.255.255 area 0
R3(config-router)#network 30.0.0.0 0.255.255.255 area 0
R3(config-router)#exit

*Dec  4 06:18:57.427: %OSPF-5-ADJCHG: Process 1, Nbr 20.1.1.1 on Serial3/2 from LOADING to FULL, Loading Done

R4(config)#router ospf 1
R4(config-router)#network 4.0.0.0 0.255.255.255 area 0
R4(config-router)#network 40.0.0.0 0.255.255.255 area 0
R4(config-router)#exit

*Dec  4 06:19:45.519: %OSPF-5-ADJCHG: Process 1, Nbr 20.1.1.1 on Serial3/1 from LOADING to FULL, Loading Done

R5(config)#ip route 4.0.0.0 255.0.0.0  5.5.5.2
R5(config)#ip route 3.0.0.0 255.0.0.0  5.5.5.2
R5(config)#ip route 20.0.0.0 255.0.0.0  5.5.5.2
R5(config)#ip route 30.0.0.0 255.0.0.0  5.5.5.2
R5(config)#ip route 40.0.0.0 255.0.0.0  5.5.5.2
R5(config)#ip route 10.0.0.0 255.0.0.0  5.5.5.2
R5(config)#ip route 1.0.0.0 255.0.0.0  5.5.5.2
R5(config)#end


R2(config)#ip route 0.0.0.0 0.0.0.0 5.5.5.1


R2(config)#router ospf 1
R2(config-router)#default-information originate always
R2(config-router)#end



R1#show ip route ospf
Codes: L - local, 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
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       + - replicated route, % - next hop override

Gateway of last resort is 1.1.1.2 to network 0.0.0.0

O*E2  0.0.0.0/0 [110/1] via 1.1.1.2, 00:01:58, Serial3/0
O     3.0.0.0/8 [110/128] via 1.1.1.2, 00:01:58, Serial3/0
O     4.0.0.0/8 [110/128] via 1.1.1.2, 00:01:58, Serial3/0
O     20.0.0.0/8 [110/65] via 1.1.1.2, 00:01:58, Serial3/0
O     30.0.0.0/8 [110/129] via 1.1.1.2, 00:01:58, Serial3/0
O     40.0.0.0/8 [110/129] via 1.1.1.2, 00:01:58, Serial3/0


R2#show ip route
Codes: L - local, 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
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       + - replicated route, % - next hop override

Gateway of last resort is 5.5.5.1 to network 0.0.0.0

S*    0.0.0.0/0 [1/0] via 5.5.5.1
      1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        1.0.0.0/8 is directly connected, Serial3/0
L        1.1.1.2/32 is directly connected, Serial3/0
      3.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        3.0.0.0/8 is directly connected, Serial3/2
L        3.3.3.2/32 is directly connected, Serial3/2
      4.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        4.0.0.0/8 is directly connected, Serial3/1
L        4.4.4.2/32 is directly connected, Serial3/1
      5.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        5.0.0.0/8 is directly connected, Serial3/3
L        5.5.5.2/32 is directly connected, Serial3/3
O     10.0.0.0/8 [110/65] via 1.1.1.1, 00:02:20, Serial3/0
      20.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        20.0.0.0/8 is directly connected, FastEthernet0/0
L        20.1.1.1/32 is directly connected, FastEthernet0/0
O     30.0.0.0/8 [110/65] via 3.3.3.1, 00:02:20, Serial3/2
O     40.0.0.0/8 [110/65] via 4.4.4.1, 00:02:20, Serial3/1



R3#show ip route
Codes: L - local, 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
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       + - replicated route, % - next hop override

Gateway of last resort is 3.3.3.2 to network 0.0.0.0

O*E2  0.0.0.0/0 [110/1] via 3.3.3.2, 00:03:42, Serial3/2
O     1.0.0.0/8 [110/128] via 3.3.3.2, 00:03:42, Serial3/2
      3.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        3.0.0.0/8 is directly connected, Serial3/2
L        3.3.3.1/32 is directly connected, Serial3/2
O     4.0.0.0/8 [110/128] via 3.3.3.2, 00:03:42, Serial3/2
O     10.0.0.0/8 [110/129] via 3.3.3.2, 00:03:42, Serial3/2
O     20.0.0.0/8 [110/65] via 3.3.3.2, 00:03:42, Serial3/2
      30.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        30.0.0.0/8 is directly connected, FastEthernet0/0
L        30.1.1.1/32 is directly connected, FastEthernet0/0
O     40.0.0.0/8 [110/129] via 3.3.3.2, 00:03:42, Serial3/2


R4#show ip route
Codes: L - local, 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
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       + - replicated route, % - next hop override

Gateway of last resort is 4.4.4.2 to network 0.0.0.0

O*E2  0.0.0.0/0 [110/1] via 4.4.4.2, 00:03:58, Serial3/1
O     1.0.0.0/8 [110/128] via 4.4.4.2, 00:03:58, Serial3/1
O     3.0.0.0/8 [110/128] via 4.4.4.2, 00:03:58, Serial3/1
      4.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        4.0.0.0/8 is directly connected, Serial3/1
L        4.4.4.1/32 is directly connected, Serial3/1
O     10.0.0.0/8 [110/129] via 4.4.4.2, 00:03:58, Serial3/1
O     20.0.0.0/8 [110/65] via 4.4.4.2, 00:03:58, Serial3/1
O     30.0.0.0/8 [110/129] via 4.4.4.2, 00:03:58, Serial3/1
      40.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        40.0.0.0/8 is directly connected, FastEthernet0/0
L        40.1.1.1/32 is directly connected, FastEthernet0/0


R5#show ip route
Codes: L - local, 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
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       + - replicated route, % - next hop override

Gateway of last resort is not set

S     1.0.0.0/8 [1/0] via 5.5.5.2
S     3.0.0.0/8 [1/0] via 5.5.5.2
S     4.0.0.0/8 [1/0] via 5.5.5.2
      5.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        5.0.0.0/8 is directly connected, Serial3/3
L        5.5.5.1/32 is directly connected, Serial3/3
S     10.0.0.0/8 [1/0] via 5.5.5.2
      15.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
C        15.0.1.0/24 is directly connected, Loopback1
L        15.0.1.1/32 is directly connected, Loopback1
C        15.0.2.0/24 is directly connected, Loopback2
L        15.0.2.1/32 is directly connected, Loopback2
C        15.0.3.0/24 is directly connected, Loopback3
L        15.0.3.1/32 is directly connected, Loopback3
S     20.0.0.0/8 [1/0] via 5.5.5.2
S     30.0.0.0/8 [1/0] via 5.5.5.2
S     40.0.0.0/8 [1/0] via 5.5.5.2
      50.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        50.0.0.0/8 is directly connected, FastEthernet0/0
L        50.1.1.1/32 is directly connected, FastEthernet0/0


R1#ping 15.0.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 15.0.1.1, timeout is 2 seconds:
!!!!!

R2#ping 15.0.2.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 15.0.2.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 56/81/120 ms

R3#ping 15.0.3.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 15.0.3.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 68/105/156 ms


R4#ping 50.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 50.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 108/148/168 ms



R5#ping 10.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 96/163/200 ms

R5#ping 20.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 20.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 60/69/84 ms

R5#ping 30.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 30.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 112/172/244 ms

R5#ping 40.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 40.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 92/129/164 ms



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