Maipu Administration Guide

Configure an OSPF Totally Stub Area

Network Requirements

Configure OSPF for all devices, and divide the devices into three areas: Area 0, Area 1, and Area 2. Configure Area 1 as a totally Stub area.
On Device4, redistribute a static route to OSPF. After the configuration is completed, the totally Stub area cannot learn inter-area routes and external routes, while the devices of other areas can learn inter-area routes and external routes.

Network Topology

Networking for Configuring an OSPF Totally Stub Area

Figure 7-8 Networking for Configuring an OSPF Totally Stub Area

Configuration Steps

Step 1: Create VLANs, and add ports to the required VLANs. (Omitted)

Step 2: Configure IP addresses for the ports. (Omitted)

Step 3: Configure an OSPF process and let the interfaces cover the related areas.

#Configure Device1.

Configure Area 1 to a Stub area.

Device1#configure terminal
Device1(config)#router ospf 100
Device1(config-ospf)#router-id 1.1.1.1
Device1(config-ospf)#area 1 stub
Device1(config-ospf)#network 10.0.0.0 0.0.0.255 area 1
Device1(config-ospf)#network 100.0.0.0 0.0.0.255 area 1
Device1(config-ospf)#exit

#Configure Device2.

Configure Area 1 to a totally Stub area. Devce2 is an ABR, and the no-summary command takes effect only on an ABR.

Device2#configure terminal
Device2(config)#router ospf 100
Device2(config-ospf)#router-id 2.2.2.2
Device2(config-ospf)#area 1 stub no-summary
Device2(config-ospf)#network 10.0.0.0 0.0.0.255 area 1
Device2(config-ospf)#network 20.0.1.0 0.0.0.255 area 0
Device2(config-ospf)#exit

#Configure Device3.

Device3#configure terminal
Device3(config)#router ospf 100
Device3(config-ospf)#router-id 3.3.3.3
Device3(config-ospf)#network 20.0.0.0 0.0.0.255 area 0
Device3(config-ospf)#network 30.0.0.0 0.0.0.255 area 2
Device3(config-ospf)#exit

#Configure Device4.

Device4#configure terminal
Device4(config)#router ospf 100
Device4(config-ospf)#router-id 4.4.4.4
Device4(config-ospf)#network 30.0.0.0 0.0.0.255 area 2
Device4(config-ospf)#network 110.0.0.0 0.0.0.255 area 2
Device4(config-ospf)#exit

Step 4: On Device4, configure a static route, and redistribute the route into the OSPF.

#Configure Device4.

Device4(config)#ip route 200.1.1.0 255.255.255.0 110.0.0.2
Device4(config)#router ospf 100
Device4(config-ospf)#redistribute static
Device4(config-ospf)#exit

Step 5: Check the result.

#Query the OSPF LSDB and routing table of Device1.

Device1#show ip ospf database  
 
            OSPF Router with ID (1.1.1.1) (Process ID 100) 
 
                Router Link States (Area 1 [Stub]) 
Link ID   ADV Router  Age Seq#       CkSum  Link count
1.1.1.1   1.1.1.1     19  0x80000009 0x8513  2  
2.2.2.2   2.2.2.2     22  0x80000005 0x51b6  1  
 
                Net Link States (Area 1 [Stub]) 
Link ID   ADV Router  Age Seq#       CkSum
10.0.0.2  2.2.2.2     22  0x80000001 0x61ba  
 
                Summary Link States (Area 1 [Stub]) 
Link ID   ADV Router  Age Seq#       CkSum  Route
0.0.0.0   2.2.2.2     55  0x80000002 0x73c1 0.0.0.0/0  
 
Device1#show ip route  
Codes: C - connected, S - static, R - RIP, O - OSPF, OE-OSPF External, M Management 
       D - Redirect, E - IRMP, EX - IRMP external, o - SNSP, B BGP, i-ISIS  
 
Gateway of last resort is 10.0.0.2 to network 0.0.0.0 
 
O 0.0.0.0/0 [110/2] via 10.0.0.2, 00:00:19, vlan3 
C 10.0.0.0/24 is directly connected, 00:01:04, vlan3
C 100.0.0.0/24 is directly connected, 00:11:55, vlan2
C 127.0.0.0/8 is directly connected, 30:46:57, lo0

According to the information in the OSPF database, only Area 1 has an LSA for inter-area route 0.0.0.0/0, while the other areas do not have LSAs for inter-area or external routes. The ABR in the Stub area generates an inter-area route 0.0.0.0/0, which floods in the totally Stub area. Data is forwarded to outside of the area or AS through the default route.

#Query the routing table of Device2.

Device2#show ip route  
Codes: C - connected, S - static, R - RIP, O - OSPF, OE-OSPF External, M Management 
       D - Redirect, E - IRMP, EX - IRMP external, o - SNSP, B BGP, i-ISIS  
 
Gateway of last resort is not set 
 
C 10.0.0.0/24 is directly connected, 00:01:02, vlan2
C 20.0.0.0/24 is directly connected, 00:00:59, vlan3
O 30.0.0.0/24 [110/2] via 20.0.0.2, 00:00:17, vlan3
O 100.0.0.0/24 [110/2] via 10.0.0.1, 00:00:10, vlan2
O 110.0.0.0/24 [110/3] via 20.0.0.2, 00:00:17, vlan3
C 127.0.0.0/8 is directly connected, 56:07:04, lo0 
OE 200.1.1.0/24 [150/20] via 20.0.0.2, 00:00:16, vlan3

According to the queried information, you will find that Device2 is able to learn inter-area and external routes.

If you run the area area-id stub command but do not run the no-summary command, the device in the area can learn inter-area routes but cannot learn external routes. Access to a network outside the AS is still conducted through the default route.