Typical Configuration Of OSPF Stub Area on AR28、AR46 Series Routers

Typical Configuration Of OSPF Stub Area on AR28、AR46 Series Routers

[Requirements]

In an OSPF AS, Routers A and B run in area 0; Routers B and C run in area 1 (Stub area); Router B serves as the ABR. Router A imports an external route to D. No Type-5 external routers to D exist in area Area 1 accesses D through the default route advertised by the ABR.

[Networking diagram]

[Configuration script]

Configuration script on Router A

# sysname RouterA # router id 1.1.1.1 # radius scheme system # domain system # interface Ethernet0/0 ip address 10.1.1.1 255.255.255.0 # interface Ethernet1/0/1 ip address 50.1.1.2 255.255.255.0 # interface Serial0/0 link-protocol ppp ip address 20.1.1.1 255.255.255.252 # interface NULL0 # interface LoopBack0 ip address 1.1.1.1 255.255.255.255 # ospf 1 import-route static         /Import the static route/ area 0.0.0.0 network 1.1.1.1 0.0.0.0 network 10.1.1.0 0.0.0.255 network 20.1.1.0 0.0.0.3 # ip route-static 100.1.1.0 255.255.255.0 50.1.1.1 preference 60 /Configure the static route to 100.1.1.0/24/ # user-interface con 0 user-interface vty 0 4 # return

Configuration script on Router B

# sysname RouterB # router id 1.1.1.2 # radius scheme system # domain system # interface Seria0/0 link-protocol ppp ip address 20.1.1.2 255.255.255.252 # interface Serial0/1 link-protocol ppp ip address 30.1.1.1 255.255.255.252 # interface NULL0 # interface LoopBack0 ip address 1.1.1.2 255.255.255.255 # ospf 1 area 0.0.0.1 network 30.1.1.0 0.0.0.3 stub                            /Configure area 1 to Stub area/ # area 0.0.0.0 network 1.1.1.2 0.0.0.0 network 20.1.1.0 0.0.0.3 # user-interface con 0 user-interface vty 0 4 # return

Configuration script on Router C

# sysname RouterC # router id 1.1.1.3 # radius scheme system # domain system # interface Ethernet0/0 ip address 40.1.1.1 255.255.255.0 # interface Ethernet1/0/1 ip address 40.1.2.1 255.255.255.0 # interface Serial0/0 link-protocol ppp ip address 30.1.1.2 255.255.255.252 # interface NULL0 # interface LoopBack0 ip address 1.1.1.3 255.255.255.255 # ospf 1 area 0.0.0.1 network 1.1.1.3 0.0.0.0 network 30.1.1.0 0.0.0.3 network 40.1.1.0 0.0.0.255 network 40.1.2.0 0.0.0.255 stub                          /Configure area 1 to Stub area/ # user-interface con 0 user-interface vty 0 4 # return

 

[Verification]

Routers can learn the routes of the whole network through OSPF, and their network segments can be pinged mutually.

Routing table of Router C:

[RouterC]disp ip routing-table                                         

 Routing Table: public net                                                    

Destination/Mask   Protocol Pre  Cost        Nexthop         Interface        

0.0.0.0/0          OSPF     10   1563        30.1.1.1        Serial0/0       

1.1.1.1/32         OSPF     10   3125        30.1.1.1        Serial0/0       

1.1.1.2/32         OSPF     10   1563        30.1.1.1        Serial0/0       

1.1.1.3/32         DIRECT   0    0           127.0.0.1       InLoopBack0     

10.1.1.0/24        OSPF     10   3125        30.1.1.1        Serial2/0/0     

20.1.1.0/30        OSPF     10   3124        30.1.1.1        Serial2/0/0     

30.1.1.0/30        DIRECT   0    0           30.1.1.2        Serial2/0/0     

30.1.1.1/32        DIRECT   0    0           30.1.1.1        Serial2/0/0     

30.1.1.2/32        DIRECT   0    0           127.0.0.1       InLoopBack0     

40.1.1.0/24        DIRECT   0    0           40.1.1.1        Ethernet0/0     

40.1.1.1/32        DIRECT   0    0           127.0.0.1       InLoopBack0     

40.1.2.0/24        DIRECT   0    0           40.1.2.1        Ethernet0/1     

40.1.2.1/32        DIRECT   0    0           127.0.0.1       InLoopBack0     

127.0.0.0/8        DIRECT   0    0           127.0.0.1       InLoopBack0     

127.0.0.1/32       DIRECT   0    0           127.0.0.1       InLoopBack0     

[Tip]

1. Stub area is a special OSPF area, which does not receive or spread Type-5 LSAs (AS-external-LSAs). For a network with a great number of Type-5 LSAs, this method can effectively reduce the LSDB size of router in the Stub area and mitigate the resource utilization of SPF calculation for the router. In general, the Stub area is located at the AS border.

2. To guarantee that the packets in the Stub area can be correctly forwarded outside the AS, the ABR in the Stub area will advertise a default route to the local area through the Summary-LSA. This route is spread in the local area only.