OSPF area commands

area

Syntax

[no] area area-id

Context

config>router>ospf

config>router>ospf3

Platforms

Supported on all 7210 SAS platforms as described in this document

Description

Commands in this context configure an OSPF or OSPF3 area. An area is a collection of network segments within an AS that have been administratively grouped together. The area ID can be specified in dotted decimal notation or as a 32-bit decimal integer.

The no form of this command deletes the specified area from the configuration. Deleting the area also removes the OSPF configuration of all the interfaces, virtual links, address ranges, and so on, that are currently assigned to this area.

Default

no area

Parameters

area-id

Specifies the OSPF area ID, expressed in dotted decimal notation or as a 32-bit decimal integer.

Values

0.0.0.0 to 255.255.255.255 (dotted decimal)

0 to 4294967295 (decimal integer)

area-range

Syntax

area-range ip-prefix/mask [advertise | not-advertise]

no area-range ip-prefix/mask

no area-range ipv6-prefix/prefix-length

area-range ipv6-prefix/prefix-length [advertise | not-advertise]

Context

config>router>ospf>area

config>router>ospf>area>nssa

config>router>ospf3>area

config>router>ospf3>area>nssa

Platforms

Supported on all 7210 SAS platforms as described in this document

Description

This command creates ranges of addresses on an Area Border Router (ABR) for the purpose of route summarization or suppression. When a range is created, the range is configured to be advertised or not advertised into other areas. Multiple range commands may be used to summarize or hide different ranges. In the case of overlapping ranges, the most specific range command applies.

ABRs send summary link advertisements to describe routes to other areas. To minimize the number of advertisements that are flooded, you can summarize a range of IP addresses and send reachability information about these addresses in an LSA.

The no form of this command deletes the range advertisement or non-advertisement.

Default

no area-range

Special Cases

NSSA Context

In the NSSA context, the option specifies that the range applies to external routes (via type-7 LSAs) learned within the NSSA when the routes are advertised to other areas as type-5 LSAs.

Area Context

If this command is not entered under the NSSA context, the range applies to summary LSAs even if the area is an NSSA.

Parameters

ip-prefix

Specifies the IP prefix in dotted decimal notation for the range used by the ABR.

Values

ip-prefix/mask:

ip-prefix a.b.c.d (host bits must be 0)

ipv6-prefix:

x:x:x:x:x:x:x:x (eight 16-bit pieces)

x:x:x:x:x:x:d.d.d.d

x: [0 to FFFF]H

d: [0 to 255]D

prefix-length:0 to 128

mask

Specifies the subnet mask for the range.

Values

0 to 32 (mask length)

advertise | not-advertise

Specifies whether to advertise the summarized range of addresses into other areas. The advertise keyword indicates the range is advertised, and the not-advertise keyword indicates the range is not advertised.

Default

advertise

blackhole-aggregate

Syntax

[no] blackhole-aggregate

Context

config>router>ospf>area

config>router>ospf3>area

Platforms

Supported on all 7210 SAS platforms as described in this document

Description

This command installs a low-priority blackhole route for the entire aggregate. Existing routes that make up the aggregate have a higher priority and only the components of the range for which no route exists are blackholed.

It is possible that when performing area aggregation, addresses may be included in the range for which no actual route exists. This can cause routing loops. To avoid this problem configure the blackhole aggregate option.

The no form of this command removes this option.

Default

blackhole-aggregate

default-metric

Syntax

default-metric metric

no default-metric

Context

config>router>ospf>area>stub

config>router>ospf3>area

Platforms

Supported on all 7210 SAS platforms as described in this document

Description

This command configures the metric used by the ABR for the default route into a stub area.

The default metric should only be configured on an ABR of a stub area.

An ABR generates a default route if the area is a stub area.

The no form of this command reverts to the default value.

Default

default-metric 1

Parameters

metric

Specifies the metric, expressed as a decimal integer, for the default route cost to be advertised into the stub area.

Values

1 to 16777215

lfa-policy-map

Syntax

lfa-policy-map route-nh-template template-name

no lfa-policy-map

Context

config>router>ospf>area>interface

Platforms

Supported on all 7210 SAS platforms as described in this document

Description

This command applies a route next-hop policy template to an OSPF interface. When a route next-hop policy template is applied to an interface in OSPF, it is applied in all areas.

The command in an OSPF interface context can only be executed under the area in which the specified interface is primary, and then applied in that area and in all other areas where the interface is secondary. If the user attempts to apply it to an area where the interface is secondary, the command fails.

If the user excluded the interface from LFA using the command loopfree-alternate-exclude, the LFA policy, if applied to the interface, has no effect.

If the user applied a route next-hop policy template to a loopback interface or to the system interface, the command is not rejected, but the policy has no effect on the interface.

The no form of this command deletes the mapping of a route next-hop policy template to an OSPF interface.

Parameters

template-name

Specifies the name of the template, 32 characters maximum.

loopfree-alternate-exclude

Syntax

[no] loopfree-alternate-exclude

Context

config>router>ospf>area

config>router>ospf>area>interface

config>router>ospf3>area>interface

Platforms

Supported on all 7210 SAS platforms as described in this document

Description

This command instructs IGP to exclude a specific interface or all interfaces that are participating in a specific OSPF area in the SPF LFA computation. This reduces LFA SPF calculation where it is not needed.

When an interface is excluded from the LFA SPF in OSPF, it is excluded in all areas. However, the loopfree-alternate-exclude command can only be executed under the area in which the specified interface is primary. If the command is enabled, the interface is excluded in that area and in all other areas where the interface is secondary. If the user attempts to apply it to an area where the interface is secondary, the command fail.

The no form of this command reverts to the default value.

Default

no loopfree-alternate-exclude

nssa

Syntax

[no] nssa

Context

config>router>ospf>area

config>router>ospf3>area

Platforms

Supported on all 7210 SAS platforms as described in this document

Description

Commands in this context configure an OSPF or OSPF3 Not So Stubby Area (NSSA) and adds or removes the NSSA designation from the area.

NSSAs are similar to stub areas in that no external routes are imported into the area from other OSPF areas. The major difference between a stub area and an NSSA is an NSSA has the capability to flood external routes that it learns throughout its area and via an ABR to the entire OSPF or OSPF3 domain.

Existing virtual links of a non-stub or NSSA are removed when the designation is changed to NSSA or stub.

An area can be designated as stub or NSSA but never both at the same time.

By default, an area is not configured as an NSSA.

The no form of this command removes the NSSA designation and configuration context from the area.

Default

no nssa

originate-default-route

Syntax

originate-default-route [type-7]

no originate-default-route

Context

config>router>ospf>area>nssa

config>router>ospf3>area>nssa

Platforms

Supported on all 7210 SAS platforms as described in this document

Description

This command enables the generation of a default route and its LSA type (3 or 7) into an NSSA by an NSSA ABR or ASBR.

When configuring an NSSA with no summaries, the ABR injects a type 3 LSA default route into the NSSA. Some older implementations expect a type 7 LSA default route.

The no form of this command disables origination of a default route.

Default

no originate-default-route

Parameters

type-7

Specifies that a type-7 LSA should be used for the default route.

Configure this parameter to inject a type-7 LSA default route instead of the type-3 LSA into the NSSA configured with no summaries.

To revert to a type-3 LSA, enter originate-default-route without the type-7 parameter.

Default

type-3 LSA for the default route

redistribute-external

Syntax

[no] redistribute-external

Context

config>router>ospf>area>nssa

config>router>ospf3>area>nssa

Platforms

Supported on all 7210 SAS platforms as described in this document

Description

This command enables the redistribution of external routes into an NSSA or an NSSA ABR that is exporting the routes into non-NSSA areas.

NSSAs are similar to stub areas in that no external routes are imported into the area from other OSPF or OSPF3 areas. The major difference between a stub area and an NSSA is that the NSSA has the capability to flood external routes that it learns (providing it is an ASBR) throughout its area and via an ABR to the entire OSPF or OSPF3 domain.

The no form of this command disables the default behavior to automatically redistribute external routes into the NSSA from the NSSA ABR.

Default

redistribute-external

stub

Syntax

[no] stub

Context

config>router>ospf>area

config>router>ospf3>area

Platforms

Supported on all 7210 SAS platforms as described in this document

Description

This command adds or removes the stub designation from an OSPF or OSPF3 area. Commands in this context configure the OSPF or OSPF3 stub area.

External routing information is not flooded into stub areas. All routers in the stub area must be configured with the stub command. An OSPF or OSPF3 area cannot be both an NSSA and a stub area.

Existing virtual links of a non-stub area or NSSA are removed when its designation is changed to NSSA or stub.

By default, an area is not a stub area.

The no form of this command removes the stub designation and configuration context from the area.

Default

no stub

summaries

Syntax

[no] summaries

Context

config>router>ospf>area>stub

config>router>ospf>area>nssa

config>router>ospf3>area>stub

config>router>ospf3>area>nssa

Platforms

Supported on all 7210 SAS platforms as described in this document

Description

This command enables sending summary (type 3) advertisements into a stub area or NSSA on an ABR.

This command is particularly useful to reduce the size of the routing and Link State Database (LSDB) tables within the stub area or NSSA.

By default, summary route advertisements are sent into the stub area or NSSA.

The no form of this command disables sending summary route advertisements and, for stub areas, only the default route is advertised by the ABR.

Default

summaries