nssa (OSPFv3)
Function
The nssa command configures an OSPFv3 area as an not-so-stubby area (NSSA).
The undo nssa command cancels the configuration.
Format
nssa [ default-route-advertise [ cost cost | type type | tag tag ] * | no-import-route | no-summary | translator-always | translator-interval translator-interval | set-n-bit | suppress-forwarding-address ] *
undo nssa
Parameters
| Parameter | Description | Value |
|---|---|---|
| default-route-advertise | Generates default Type-7 LSAs on the ASBR and then advertises
them to the NSSA. NOTE:
The ABR generates a default NSSA
LSA (Type–7 LSA) automatically and advertises it in the NSSA. |
- |
| cost cost | Specifies the default cost of Type 7 LSAs. | It is an integer ranging from 1 to 16777214. The default value is 1. |
| type type | Specifies the default type of Type 5 LSAs. | The value is an integer ranging from 1 to 2.
By default, it is 2. |
| tag tag | Specifies the tag value of the OSPFv3 route imported to an NSSA. | It is an integer ranging from 0 to 4294967295. The default value is 0. |
| no-import-route | Indicates that no external routes are imported to NSSAs. | - |
| no-summary | Disables ABRs from sending summary LSAs to NSSAs. | - |
| translator-always | Specifies the ABR in an NSSA as the translator. Multiple ABRs in an NSSA can be configured as translators. | - |
| translator-interval translator-interval | Specifies the timeout period of a translator. | It is an integer ranging from 1 to 120, in seconds. The default value is 40 seconds. |
| set-n-bit | Indicates that the N-bit is set in DD packets. | - |
| suppress-forwarding-address | Enables the device to suppress the forwarding address of a Type 5 LSA translated from a Type 7 LSA. | - |
Usage Guidelines
To connect routers to an NSSA, you must use the nssa command to configure NSSA attributes for the area to which the routers belong.
The area may be updated after NSSA attributes are configured or deleted. Therefore, the NSSA attributes can be re-configured or deleted only after the last update of NSSA attributes is complete.
The keyword default-route-advertise is used to generate default Type 7 LSAs. Regardless of whether there is route ::/0 in the routing table on an ABR, a Type 7 LSA default route is generated. A Type 7 LSA default route can be generated only when there is route ::/0 in the routing table on an ASBR.
When an ASBR is also an ABR, you can specify no-import-route to disable OSPFv3 from advertising the external routes imported through the import-route command to NSSAs. To reduce the number of LSAs to be transmitted to NSSAs, you can specify no-summary on an ABR to disable the ABR from transmitting summary LSAs (Type 3 LSAs) to NSSAs.
When the LS age field (aging time) in the LSA header reaches 3600 seconds, this LSA is deleted.
After the keyword set-n-bit is set, a router re-establishes neighbor relationships with routers directly connected to it in the NSSA.