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CX11x, CX31x, CX710 (Earlier Than V6.03), and CX91x Series Switch Modules V100R001C10 Configuration Guide 13

The documents describe the configuration of various services supported by the CX11x&CX31x&CX91x series switch modules The description covers configuration examples and function configurations.

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Usage Scenario

Usage Scenario

This section describes usage scenarios of routing policies.

Specific Routes Filtering

On the OSPF-enabled network shown in Figure 7-124, RouterA receives routes from the Internet and advertises some of the routes to RouterB.

  • RouterA advertises only routes 172.1.17.0/24, 172.1.18.0/24, and 172.1.19.0/24 to RouterB.

  • RouterC accepts only the route 172.1.18.0/24.

  • RouterD accepts all the routes advertised by RouterB.

Figure 7-124 Networking diagram for filtering received and advertised routes

There are multiple approaches to meet the preceding requirements, and the following two approaches are used in this example:
  • Use IP prefix lists

    • Configure an IP prefix list on RouterA and configure the IP prefix list as an export policy of RouterA to be used by OSPF.
    • Configure another IP prefix list on RouterC and configure the IP prefix list as an import policy of RouterC to be used by OSPF.
  • Use route-policies

    • Configure a Route-Policy (the matching rules can be the IP prefix list, cost, or route tag) on RouterA and configure the Route-Policy as an export policy of RouterA to be used by OSPF.
    • Configure another Route-Policy on RouterC and configure the Route-Policy as an import policy of RouterC to be used by OSPF.

    Compared with an IP prefix list, a Route-Policy allows route attributes to be modified and can be used to control routes more flexibly, but it is more complex to configure.

Transparent Transmission of Routes of Other Protocols Through an OSPF AS

On the network shown in Figure 7-125, an AS runs OSPF and functions as a transit AS for other areas. Routes from the IS-IS area connected to RouterA need to be transparently transmitted through the OSPF AS to the IS-IS area connected to RouterD.

Figure 7-125 Networking diagram for transparently transmitting routes of other protocols through an OSPF AS

To meet the preceding requirements, configure a Route-Policy on RouterA to set a tag for the imported IS-IS routes. RouterD identifies the IS-IS routes from OSPF routes based on the tag.

Routing Policy Application in Inter-AS VPN Option C

On the network shown in Figure 7-126, CE1 and CE2 communicate with each other through inter-AS VPN Option C.

Figure 7-126 Networking diagram for implementing route-policies in the inter-AS VPN Option C scenario

To establish an inter-AS LSP between PE1 and PE2, route-policies need to be configured on ASBRs.
  • When an ASBR advertises the routes received from a PE in the same AS to the peer ASBR, the ASBR allocates MPLS labels to the routes using a Route-Policy.
  • When an ASBR advertises labeled IPv4 routes to a PE in the same AS, the ASBR reallocates MPLS labels to the routes using another Route-Policy.

In addition, to control route transmission between different VPN instances on a PE, configure a Route-Policy on the PE and configure the Route-Policy as an import or export policy on the VPN instances.

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Updated: 2019-12-13

Document ID: EDOC1000041694

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