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Configuration Guide - IP Unicast Routing
CloudEngine 12800 and 12800E V200R002C50

This document describes the configurations of IP Unicast Routing, including IP Routing, Static Route, RIP, RIPng, OSPF, OSPFv3, IPv4 IS-IS, IPv6 IS-IS, BGP, Routing Policy, and PBR.

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Configuring an OSPFv3 NSSA

Configuring an OSPFv3 NSSA


An excessive number of entries in a routing table cause high CPU usage. To reduce the number of entries in a routing table, configure a non-backbone area on the border of an AS as a stub area or an NSSA to reduce the amount of routing information to be transmitted. For details on how to configure an OSPFv3 stub area, see Configuring OSPF Stub Areas.

OSPFv3 stub areas cannot import or transmit external routes. If you need to import external routes to an area and prevent these routes from consuming resources, configure the area as an NSSA. NSSAs can import AS external routes and advertise them within the entire AS, without learning external routes from other areas in the AS, which reduces bandwidth and storage resource consumption on the device.

An NSSA requires NSSA attributes on all the devices in this area.

Pre-configuration Tasks

Before configuring an OSPFv3 NSSA, complete the following tasks:

  • Configure an IP address for each interface to ensure that neighboring routers can use the IP addresses to communicate with each other.
  • Configure basic OSPFv3 functions.


  1. Run system-view

    The system view is displayed.

  2. Run ospfv3 [ process-id ]

    The OSPFv3 process view is displayed.

  3. Run area area-id

    The OSPFv3 area view is displayed.

  4. Run nssa [ default-route-advertise [ cost cost | type type | tag tag ] * | no-import-route | no-summary | translator-always | translator-interval translator-interval | set-n-bit ] *

    The specified area is configured as an NSSA.

    The usage scenarios of the nssa command are as follows:

    • If default-route-advertise is set, Type 7 LSAs carrying the default route will be generated, regardless of whether the route ::/0 exists in the routing table on an ABR; such LSAs are generated only when the route ::/0 exists in the routing table on an ASBR.

    • If an ASBR also functions as an ABR, setting no-import-route prevents external routes imported using the import-route command from being advertised to the NSSA.
    • To reduce the number of LSAs to be transmitted to the NSSA, set no-summary on an ABR to prevent the ABR from transmitting Summary LSAs (Type 3 LSAs) to the NSSA.
    • If set-n-bit is set, the DD packets sent by the device carry the N-bit being 1.

    • If multiple ABRs are deployed in the NSSA, the system automatically selects an ABR (generally the device with the largest router ID) as a translator to convert Type 7 LSAs into Type 5 LSAs. You can also set translator-always on an ABR to specify the ABR as an all-the-time translator. To specify two ABRs for load balancing, set translator-always on the two ABRs to specify them as all-the-time translators, which prevents LSA flooding caused by translator role changes.
    • The translator-interval parameter is used to ensure uninterrupted services when translator roles change. The value of translator-interval must be greater than the flooding interval.

  5. Run commit

    The configuration is committed.

Updated: 2019-03-21

Document ID: EDOC1000166601

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