Configuring OSPF aggregate area ranges on the router

Use aggregate area ranges to reduce the number of link-state advertisements required within the area. You can also control advertisements.

Before you begin

  • Enable OSPF globally.

  • Ensure that an area exists.

  • You configure OSPF area ranges on a VRF instance the same way you configure the GlobalRouter, except that you must use VRF Router Configuration mode and the prefix ip ospf. The VRF must have an RP Trigger of OSPF. Not all parameters are configurable on non0 VRFs.

Procedure

  1. Enter OSPF Router Configuration mode:

    enable

    configure terminal

    router ospf

  2. Configure an OSPF area range:

    area range {A.B.C.D} {A.B.C.D/X} <summary-link|nssa-extlink>

  3. Configure the advertised metric cost:

    area range {A.B.C.D} {A.B.C.D/X} <summary-link|nssa-extlink> advertise-metric <0-65535>

  4. Configure the advertisement mode:

    area range {A.B.C.D} {A.B.C.D/X} <summary-link|nssa-extlink> advertise-mode <summarize|suppress|no-summarize>

  5. Ensure that the configuration is correct:

    show ip ospf area-range [vrf WORD<1-16>] [vrfids WORD<0-512>]

Example

Configure an OSPF area range to 192.0.2.2, configure the advertised metric cost to 10, and the advertisement mode to summarize.

Switch:1>enable
Switch:1#configure terminal
Switch:1(config)#router ospf
Switch:1(config-ospf)# area range 192.0.2.2 255.255.255.0/32 summary-link
Switch:1(config-ospf)# area range 192.0.2.2 255.255.255.0/32 summary-link advertise-metric 10
Switch:1(config-ospf)# area range 192.0.2.2 255.255.255.0/32 summary-link advertise-mode summarize

Variable definitions

The following table defines parameters for the area range command.

Variable

Value

{A.B.C.D} {A.B.C.D/X}

{A.B.C.D} identifies an OSPF area and {A.B.C.D/X} is the IP address and subnet mask of the range, respectively.

advertise-metric <0-65535>

Changes the advertised metric cost of the OSPF area range.

advertise-mode <summarize|suppress|no-summarize>

Changes the advertisement mode of the range.

<summary-link|nssa-extlink>

Specifies the link-state advertisement (LSA) type. If you configure the range as type nssa-extlink, you cannot configure the advertise-metric.

The following table defines parameters for the show ip ospf area-range command.

Variable

Value

vrf WORD<1-16>

Specifies a VRF by name.

vrfids WORD<0-512>

Specifies a range of VRF IDs.
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