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Example for Filtering the Routes to Be Received or Advertised

Networking Requirements

Figure 1 shows how on an OSPF network, SwitchA receives routes from the Internet and provides these routes for the OSPF network. A user wants devices on the OSPF network to access only the network segments 172.16.17.0/24, 172.16.18.0/24, and 172.16.19.0/24, and SwitchC to access only the network segment 172.16.18.0/24.

Figure 1 Networking diagram for filtering the received and advertised routes

Device

Interface

VLANIF Interface

IP Address

SwitchA

GE0/0/1

VLANIF10

192.168.1.1/24

SwitchB

GE0/0/1

VLANIF10

192.168.1.2/24

SwitchB

GE0/0/2

VLANIF20

192.168.2.1/24

SwitchC

GE0/0/1

VLANIF20

192.168.2.2/24

Configuration Roadmap

The configuration roadmap is as follows:

  1. Configure a routing policy on SwitchA and apply the routing policy during route advertisement. When routes are advertised, the routing policy allows SwitchA to provide routes from network segments 172.16.17.0/24, 172.16.18.0/24, and 172.16.19.0/24 for SwitchB, and allows devices on the OSPF network to access the three network segments.

  2. Configure a routing policy on SwitchC and apply the routing policy during route importing. When routes are imported, the routing policy allows SwitchC to receive only the routes from the network segment 172.16.18.0/24 and access this network segment.

Procedure

  1. Add interfaces to VLANs.

    # Configure SwitchA. Ensure that the configurations of SwitchB and SwitchC are the same as the configuration of SwitchA.

    <HUAWEI> system-view
[HUAWEI] sysname SwitchA
[SwitchA] vlan batch 10
[SwitchA] interface gigabitethernet 0/0/1
[SwitchA-GigabitEthernet0/0/1] port link-type trunk
[SwitchA-GigabitEthernet0/0/1] port trunk allow-pass vlan 10
[SwitchA-GigabitEthernet0/0/1] quit

  2. Assign IP addresses to VLANIF interfaces.

    # Configure SwitchA. Ensure that the configurations of SwitchB and SwitchC are the same as the configuration of SwitchA.

    [SwitchA] interface vlanif 10
[SwitchA-Vlanif10] ip address 192.168.1.1 24
[SwitchA-Vlanif10] quit

  3. Configure basic OSPF functions.

    # Configure SwitchA.

    [SwitchA] ospf
[SwitchA-ospf-1] area 0
[SwitchA-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255
[SwitchA-ospf-1-area-0.0.0.0] quit
[SwitchA-ospf-1] quit

    # Configure SwitchB.

    [SwitchB] ospf
[SwitchB-ospf-1] area 0
[SwitchB-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255
[SwitchB-ospf-1-area-0.0.0.0] network 192.168.2.0 0.0.0.255
[SwitchB-ospf-1-area-0.0.0.0] quit
[SwitchB-ospf-1] quit

    # Configure SwitchC.

    [SwitchC] ospf
[SwitchC-ospf-1] area 0
[SwitchC-ospf-1-area-0.0.0.0] network 192.168.2.0 0.0.0.255
[SwitchC-ospf-1-area-0.0.0.0] quit
[SwitchC-ospf-1] quit

  4. Configure five static routes on SwitchA and import these routes into OSPF. 

    [SwitchA] ip route-static 172.16.16.0 24 NULL 0
[SwitchA] ip route-static 172.16.17.0 24 NULL 0
[SwitchA] ip route-static 172.16.18.0 24 NULL 0
[SwitchA] ip route-static 172.16.19.0 24 NULL 0
[SwitchA] ip route-static 172.16.20.0 24 NULL 0
[SwitchA] ospf
[SwitchA-ospf-1] import-route static
[SwitchA-ospf-1] quit

    # Check the IP routing table on SwitchB. You can see that the five static routes are imported into OSPF.

    [SwitchB] display ip routing-table
Route Flags: R - relay, D - download to fib, T - to vpn-instance
------------------------------------------------------------------------------
Routing Tables: Public
         Destinations : 11       Routes : 11

 Destination/Mask    Proto  Pre  Cost     Flags NextHop         Interface 

      127.0.0.0/8    Direct 0    0           D  127.0.0.1       InLoopBack0
      127.0.0.1/32   Direct 0    0           D  127.0.0.1       InLoopBack0
    172.16.16.0/24   O_ASE  150  1           D  192.168.1.1     Vlanif10
    172.16.17.0/24   O_ASE  150  1           D  192.168.1.1     Vlanif10
    172.16.18.0/24   O_ASE  150  1           D  192.168.1.1     Vlanif10
    172.16.19.0/24   O_ASE  150  1           D  192.168.1.1     Vlanif10
    172.16.20.0/24   O_ASE  150  1           D  192.168.1.1     Vlanif10
    192.168.1.0/24   Direct 0    0           D  192.168.1.2     Vlanif10
    192.168.1.2/32   Direct 0    0           D  127.0.0.1       Vlanif10
    192.168.2.0/24   Direct 0    0           D  192.168.2.1     Vlanif20
    192.168.2.1/32   Direct 0    0           D  127.0.0.1       Vlanif20

  5. Configure a policy for advertising routes.

    # Configure an IP prefix list named a2b on SwitchA.

    [SwitchA] ip ip-prefix a2b index 10 permit 172.16.17.0 24
[SwitchA] ip ip-prefix a2b index 20 permit 172.16.18.0 24
[SwitchA] ip ip-prefix a2b index 30 permit 172.16.19.0 24

    # Configure a policy for advertising routes on SwitchA, and use the IP prefix list a2b to filter routes.

    [SwitchA] ospf
[SwitchA-ospf-1] filter-policy ip-prefix a2b export static

    # Check the IP routing table on SwitchB. You can see that SwitchB receives only three routes defined in a2b.

    [SwitchB] display ip routing-table
Route Flags: R - relay, D - download to fib, T - to vpn-instance
------------------------------------------------------------------------------
Routing Tables: Public
         Destinations : 9        Routes : 9
 
Destination/Mask    Proto  Pre  Cost     Flags NextHop         Interface
 
      127.0.0.0/8   Direct 0    0           D  127.0.0.1       InLoopBack0
      127.0.0.1/32  Direct 0    0           D  127.0.0.1       InLoopBack0
    172.16.17.0/24  O_ASE  150  1           D  192.168.1.1     Vlanif10
    172.16.18.0/24  O_ASE  150  1           D  192.168.1.1     Vlanif10
    172.16.19.0/24  O_ASE  150  1           D  192.168.1.1     Vlanif10
    192.168.1.0/24  Direct 0    0           D  192.168.1.2     Vlanif10
    192.168.1.2/32  Direct 0    0           D  127.0.0.1       Vlanif10
    192.168.2.0/24  Direct 0    0           D  192.168.2.1     Vlanif20
    192.168.2.1/32  Direct 0    0           D  127.0.0.1       Vlanif20

  6. Configure a policy for receiving routes.

    # Configure an IP prefix list named in on SwitchC.

    [SwitchC] ip ip-prefix in index 10 permit 172.16.18.0 24

    # Configure a policy for receiving routes on SwitchC, and use the IP prefix list in to filter routes.

    [SwitchC] ospf
[SwitchC-ospf-1] filter-policy ip-prefix in import
[SwitchC-ospf-1] quit

    # Check the IP routing table on SwitchC. You can see that the IP routing table contains only one route defined in the IP prefix list in.

    [SwitchC] display ip routing-table
Route Flags: R - relay, D - download to fib, T - to vpn-instance
------------------------------------------------------------------------------
Routing Tables: Public
         Destinations : 5        Routes : 5
 
Destination/Mask    Proto  Pre  Cost     Flags NextHop         Interface
 
      127.0.0.0/8    Direct 0    0           D  127.0.0.1       InLoopBack0
      127.0.0.1/32   Direct 0    0           D  127.0.0.1       InLoopBack0
    172.16.18.0/24   O_ASE  150  1           D  192.168.2.1     Vlanif20
    192.168.2.0/24   Direct 0    0           D  192.168.2.2     Vlanif20
    192.168.2.2/32   Direct 0    0           D  127.0.0.1       Vlanif20

Configuration Files

  • Configuration file of SwitchA

    #
sysname SwitchA
#
vlan batch 10
#
interface Vlanif10
 ip address 192.168.1.1 255.255.255.0
#
interface GigabitEthernet0/0/1
 port link-type trunk
 port trunk allow-pass vlan 10
#
ospf 1
 filter-policy ip-prefix a2b export static
 import-route static
 area 0.0.0.0
  network 192.168.1.0 0.0.0.255
#
ip ip-prefix a2b index 10 permit 172.16.17.0 24
ip ip-prefix a2b index 20 permit 172.16.18.0 24
ip ip-prefix a2b index 30 permit 172.16.19.0 24
#
ip route-static 172.16.16.0 255.255.255.0 NULL0
ip route-static 172.16.17.0 255.255.255.0 NULL0
ip route-static 172.16.18.0 255.255.255.0 NULL0
ip route-static 172.16.19.0 255.255.255.0 NULL0
ip route-static 172.16.20.0 255.255.255.0 NULL0
#
return

  • Configuration file of SwitchB

    #
sysname SwitchB
#
vlan batch 10 20
#
interface Vlanif10
 ip address 192.168.1.2 255.255.255.0
#
interface Vlanif20
 ip address 192.168.2.1 255.255.255.0
#
interface GigabitEthernet0/0/1
 port link-type trunk
 port trunk allow-pass vlan 10
#
interface GigabitEthernet0/0/2
 port link-type trunk
 port trunk allow-pass vlan 20
#
ospf 1
 area 0.0.0.0
  network 192.168.1.0 0.0.0.255
  network 192.168.2.0 0.0.0.255
#
return

  • Configuration file of SwitchC

    #
sysname SwitchC
#
vlan batch 20
#
interface Vlanif20
 ip address 192.168.2.2 255.255.255.0
#
interface GigabitEthernet0/0/1
 port link-type trunk
 port trunk allow-pass vlan 20
#
ospf 1
 filter-policy ip-prefix in import
 area 0.0.0.0
  network 192.168.2.0 0.0.0.255
#
ip ip-prefix in index 10 permit 172.16.18.0 24
#
return
Parent Topic: Configuration Examples for Routing Policies
Copyright © Huawei Technologies Co., Ltd.
Copyright © Huawei Technologies Co., Ltd.
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