area nssa
(OSPFv2)
Creates a not-so-stubby area (NSSA) or modifies its parameters.
Syntax
area
{
ip-addr
|
decimal
}
nssa
{
metric
[
no-summary
]
|
default-information-originate
}
Command Default
No areas are created.
Parameters
-
ip-addr
- Area address in IP address format.
-
decimal
- Area address In decimal format.
-
metric
- Additional cost for using a route to or from this area.
-
no-summary
- When configured on the NSSA area border router (ABR), this parameter prevents any Type 3 and Type 4 summary link-state advertisement (LSA) from being injected into the area. The only exception is that a default route is injected into the NSSA by the ABR, and strictly as a Type 3 LSA (not a Type 7, because that could cause intra-AS traffic to get routed out the AS). This makes the NSSA an NSSA totally stubby area, which can only have Type 1, 2 and 7 LSAs.
Note: This parameter is disabled by default, which means the default route must use a Type 7 LSA.
-
default-information-originate
- When configured on the ABR, this parameter injects a Type 7 default route into the NSSA area. As a result, the other NSSA routers install the default route through the advertising NSSA ABR. By default the NSSA ABR does not originate a default route to the NSSA.
Modes
OSPF router configuration mode
OSPF router VRF configuration mode
Usage Guidelines
NSSAs are typically needed when one-way transmission of Type-5 LSAs (out of the area) is desired but injection of the same LSAs into the area is not acceptable.
Once created, the type of the area cannot be changed. The only exception to this rule is that an NSSA or stub area can be changed to a totally NSSA or a totally stub area, respectively.
The
no
form of the command deletes a NSSA.
Examples
The following example sets an additional cost of 5 on an NSSA identified as 2, includes the no-summary parameter, and prevents the device from importing type 3 and type 4 summary LSAs into the NSSA area.
device# configure terminal
device(config)# router ospf
device(config-router-ospf-vrf-default-vrf)# area 2 nssa 5 no-summary
