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CLI-based Configuration Guide - IP Unicast Routing
AR100, AR120, AR150, AR160, AR200, AR1200, AR2200, AR3200, and AR3600 V200R009
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Example for Configuring OSPF Stub Areas

Example for Configuring OSPF Stub Areas

Networking Requirements

As shown in Figure 5-38, all routers run OSPF, and the entire AS is divided into three areas. Router A and Router B serve as ABRs to forward routes between areas. Router D serves as an ASBR to import external routes (static routes).

It is required to configure Area 1 as a stub area to reduce the LSAs advertised to this area without affecting the route reachability.

Figure 5-38 Configuring OSPF stub areas

Configuration Roadmap

The configuration roadmap is as follows:

  1. Enable OSPF on each router, and configure basic OSPF functions.

  2. Configure static routes on Router D, and import them into OSPF.

  3. Configure Area 1 as a stub area, and check the OSPF routing information on Router C.

  4. Stop Router A from advertising Type 3 LSAs to the stub area, and check the OSPF routing information on Router C.

Procedure

  1. Configure an IP address for each interface.

    # Configure Router A.

    <Huawei> system-view
    [Huawei] sysname RouterA
    [RouterA] interface gigabitethernet 1/0/0
    [RouterA-GigabitEthernet1/0/0] ip address 192.168.0.1 24
    [RouterA-GigabitEthernet1/0/0] quit
    [RouterA] interface gigabitethernet 2/0/0
    [RouterA-GigabitEthernet2/0/0] ip address 192.168.1.1 24
    [RouterA-GigabitEthernet2/0/0] quit

    The configurations of Router B, Router C, Router D, Router E, and Router F are similar to the configuration of Router A, and are not mentioned here.

  2. Configure basic OSPF functions.

    # Configure Router A.

    [RouterA] router id 1.1.1.1
    [RouterA] ospf
    [RouterA-ospf-1] area 0
    [RouterA-ospf-1-area-0.0.0.0] network 192.168.0.0 0.0.0.255
    [RouterA-ospf-1-area-0.0.0.0] quit
    [RouterA-ospf-1] area 1
    [RouterA-ospf-1-area-0.0.0.1] network 192.168.1.0 0.0.0.255
    [RouterA-ospf-1-area-0.0.0.1] quit
    [RouterA-ospf-1] quit

    # Configure Router B.

    [RouterB] router id 2.2.2.2
    [RouterB] ospf
    [RouterB-ospf-1] area 0
    [RouterB-ospf-1-area-0.0.0.0] network 192.168.0.0 0.0.0.255
    [RouterB-ospf-1-area-0.0.0.0] quit
    [RouterB-ospf-1] area 2
    [RouterB-ospf-1-area-0.0.0.2] network 192.168.2.0 0.0.0.255
    [RouterB-ospf-1-area-0.0.0.2] quit
    [RouterB-ospf-1] quit

    # Configure Router C.

    [RouterC] router id 3.3.3.3
    [RouterC] ospf
    [RouterC-ospf-1] area 1
    [RouterC-ospf-1-area-0.0.0.1] network 192.168.1.0 0.0.0.255
    [RouterC-ospf-1-area-0.0.0.1] network 172.16.1.0 0.0.0.255
    [RouterC-ospf-1-area-0.0.0.1] quit
    [RouterC-ospf-1] quit

    # Configure Router D.

    [RouterD] router id 4.4.4.4
    [RouterD] ospf
    [RouterD-ospf-1] area 2
    [RouterD-ospf-1-area-0.0.0.2] network 192.168.2.0 0.0.0.255
    [RouterD-ospf-1-area-0.0.0.2] network 172.17.1.0 0.0.0.255
    [RouterD-ospf-1-area-0.0.0.2] quit
    [RouterD-ospf-1] quit

    # Configure Router E.

    [RouterE] router id 5.5.5.5
    [RouterE] ospf
    [RouterE-ospf-1] area 1
    [RouterE-ospf-1-area-0.0.0.1] network 172.16.1.0 0.0.0.255
    [RouterE-ospf-1-area-0.0.0.1] quit
    [RouterE-ospf-1] quit

    # Configure Router F.

    [RouterF] router id 6.6.6.6
    [RouterF] ospf
    [RouterF-ospf-1] area 2
    [RouterF-ospf-1-area-0.0.0.2] network 172.17.1.0 0.0.0.255
    [RouterF-ospf-1-area-0.0.0.2] quit
    [RouterF-ospf-1] quit

  3. Configure Router D to import static routes. 

    [RouterD] ip route-static 200.0.0.0 8 null 0
    [RouterD] ospf
    [RouterD-ospf-1] import-route static type 1
    [RouterD-ospf-1] quit

    # View ABR/ASBR information on Router C.

    [RouterC] display ospf abr-asbr
              OSPF Process 1 with Router ID 3.3.3.3
                      Routing Table to ABR and ASBR
     RtType        Destination     Area       Cost    Nexthop          Type
     Intra-area    1.1.1.1         0.0.0.1    1       192.168.1.1      ABR
     Inter-area    4.4.4.4         0.0.0.1    3       192.168.1.1      ASBR

    # View the OSPF routing table of Router C.

    When Router C is in a common area, there are AS external routes in the routing table.

    [RouterC] display ospf routing
         OSPF Process 1 with Router ID  3.3.3.3
                       Routing Tables
     Routing for Network
     Destination        Cost  Type         NextHop          AdvRouter       Area
     172.16.1.0/24      1     Transit     172.16.1.1      3.3.3.3         0.0.0.1
     172.17.1.0/24      4     Inter-area  192.168.1.1     1.1.1.1         0.0.0.1
     192.168.0.0/24     2     Inter-area  192.168.1.1     1.1.1.1         0.0.0.1
     192.168.1.0/24     1     Transit     192.168.1.2     3.3.3.3         0.0.0.1
     192.168.2.0/24     3     Inter-area  192.168.1.1     1.1.1.1         0.0.0.1
     Routing for ASEs
     Destination    Cost      Type       Tag         NextHop         AdvRouter
     200.0.0.0/8    4         Type1      1           192.168.1.1     4.4.4.4
     Total Nets: 6
     Intra Area: 2  Inter Area: 3  ASE: 1  NSSA: 0

  4. Configure Area 1 as a stub area.

    # Configure Router A.

    [RouterA] ospf
    [RouterA-ospf-1] area 1
    [RouterA-ospf-1-area-0.0.0.1] stub
    [RouterA-ospf-1-area-0.0.0.1] quit
    [RouterA-ospf-1] quit

    # Configure Router C.

    [RouterC] ospf
    [RouterC-ospf-1] area 1
    [RouterC-ospf-1-area-0.0.0.1] stub
    [RouterC-ospf-1-area-0.0.0.1] quit
    [RouterC-ospf-1] quit

    # Configure Router E.

    [RouterE] ospf
    [RouterE-ospf-1] area 1
    [RouterE-ospf-1-area-0.0.0.1] stub
    [RouterE-ospf-1-area-0.0.0.1] quit
    [RouterE-ospf-1] quit

    # View the routing table of Router C.

    After the area where Router C resides is configured as a stub area, AS external routes are invisible. Instead, there is a default route.

    [RouterC] display ospf routing
              OSPF Process 1 with Router ID 3.3.3.3
                       Routing Tables
    Routing for Network
     Destination        Cost  Type       NextHop         AdvRouter       Area
     0.0.0.0/0          2    Inter-area  192.168.1.1     1.1.1.1         0.0.0.1
     172.16.1.0/24      1    Transit     172.16.1.1      3.3.3.3         0.0.0.1
     172.17.1.0/24      4    Inter-area  192.168.1.1     1.1.1.1         0.0.0.1
     192.168.0.0/24     2    Inter-area  192.168.1.1     1.1.1.1         0.0.0.1
     192.168.1.0/24     1    Transit     192.168.1.2     3.3.3.3         0.0.0.1
     192.168.2.0/24     3    Inter-area  192.168.1.1     1.1.1.1         0.0.0.1
     Total Nets: 6
     Intra Area: 2  Inter Area: 4  ASE: 0  NSSA: 0

  5. Stop Router A from advertising Type 3 LSAs to the stub area. 

    [RouterA] ospf
    [RouterA-ospf-1] area 1
    [RouterA-ospf-1-area-0.0.0.1] stub no-summary
    [RouterA-ospf-1-area-0.0.0.1] quit
    [RouterA-ospf-1] quit

  6. Verify the configuration.

    # View the OSPF routing table of Router C.

    [RouterC] display ospf routing
              OSPF Process 1 with Router ID 3.3.3.3
                       Routing Tables
     Routing for Network
     Destination        Cost  Type       NextHop         AdvRouter       Area
     0.0.0.0/0          2   Inter-area   192.168.1.1     1.1.1.1         0.0.0.1
     172.16.1.0/24      1   Transit      172.16.1.1      3.3.3.3         0.0.0.1
     192.168.1.0/24     1   Transit      192.168.1.2     3.3.3.3         0.0.0.1
     Total Nets: 3
     Intra Area: 2  Inter Area: 1  ASE: 0  NSSA: 0

    After the advertisement of summary LSAs to a stub area is disabled, the routing entries of the stub router are further reduced, and only the default route to a destination outside the AS is reserved.

Configuration Files

  • Configuration file of Router A

    #
     sysname RouterA
    #
    router id 1.1.1.1
    #
    interface GigabitEthernet1/0/0
     ip address 192.168.0.1 255.255.255.0
    #
    interface GigabitEthernet2/0/0
     ip address 192.168.1.1 255.255.255.0
    #
    ospf 1
     area 0.0.0.0
      network 192.168.0.0 0.0.0.255
     area 0.0.0.1
      network 192.168.1.0 0.0.0.255
      stub no-summary
    #
    return

  • Configuration file of Router B

    #
     sysname RouterB
    #
    router id 2.2.2.2
    #
    interface GigabitEthernet1/0/0
     ip address 192.168.0.2 255.255.255.0
    #
    interface GigabitEthernet2/0/0
     ip address 192.168.2.1 255.255.255.0
    #
    ospf 1
     area 0.0.0.0
      network 192.168.0.0 0.0.0.255
     area 0.0.0.2
      network 192.168.2.0 0.0.0.255
    #
    return

  • Configuration file of Router C

    #
     sysname RouterC
    #
    router id 3.3.3.3
    #
    interface GigabitEthernet1/0/0
     ip address 192.168.1.2 255.255.255.0
    #
    interface GigabitEthernet2/0/0
     ip address 172.16.1.1 255.255.255.0
    #
    ospf 1
     area 0.0.0.1
      network 192.168.1.0 0.0.0.255
      network 172.16.1.0 0.0.0.255
      stub
    #
    return

  • Configuration file of Router D

    #
     sysname RouterD
    #
    router id 4.4.4.4
    #
    interface GigabitEthernet1/0/0
     ip address 192.168.2.2 255.255.255.0
    #
    interface GigabitEthernet2/0/0
     ip address 172.17.1.1 255.255.255.0
    #
    ospf 1
     import-route static type 1
     area 0.0.0.2
      network 192.168.2.0 0.0.0.255
      network 172.17.1.0 0.0.0.255
    #
    ip route-static 200.0.0.0 255.0.0.0 NULL0
    #
    return

  • Configuration file of Router E

    #
     sysname RouterE
    #
    router id 5.5.5.5
    #
    interface GigabitEthernet2/0/0
     ip address 172.16.1.2 255.255.255.0
    #
    ospf 1
     area 0.0.0.1
      network 172.16.1.0 0.0.0.255
      stub
    #
    return

  • Configuration file of Router F

    #
     sysname RouterF
    #
    router id 6.6.6.6
    #
    interface GigabitEthernet2/0/0
     ip address 172.17.1.2 255.255.255.0
    #
    ospf 1
     area 0.0.0.2
      network 172.17.1.0 0.0.0.255
    #
    return
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Updated: 2020-09-08

Document ID: EDOC1000174069

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