abr-summary

Function

The abr-summary command configures route summarization on an area border router (ABR).

The undo abr-summary command disables route summarization from an ABR.

By default, route summarization is not configured on ABRs.

Format

abr-summary ip-address mask [ [ advertise | [ cost { cost-value | inherit-minimum } ] | [ hold-max-cost hours ] | [ generate-null0-route ] ] ^* | [ not-advertise | [ cost { cost-value | inherit-minimum } ] | [ hold-max-cost hours ] ] ^* | [ generate-null0-route | [ advertise ] | [ cost { cost-value | inherit-minimum } ] | [ hold-max-cost hours ] ] ^* ]

undo abr-summary ip-address mask

Parameters

Parameter	Description	Value
ip-address	Specifies the IP address of a summary route.	The value is in dotted decimal notation.
mask	Specifies the IP address mask of the summary route.	The value is in dotted decimal notation.
advertise	Advertises the summary route. By default, the summary route is advertised.	-
cost cost-value	Specifies the cost of the summary route.	The value is an integer ranging from 0 to 16777214. By default, the largest cost of the specific routes for summarization is used as the cost of the summary route.
inherit-minimum	Indicates that the smallest cost of the specific routes for summarization is used as the cost of the summary route.	-
hold-max-cost hours	Specifies the interval at which the maximum cost is advertised in the summary route.	The value is an integer ranging from 10 to 1800, in seconds.
generate-null0-route	Generates a black-hole route in the RM module to prevent routing loops.	-
not-advertise	Prevents the summary route from being advertised. By default, the summary route is advertised.	-

Views

OSPF area view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
ospf	write

Usage Guidelines

Usage Scenario

On a large-scale OSPF network, route lookup may slow down because of the large size of the routing table. To reduce the size of the routing table and simplify management, configure route summarization.

This command enables routes with the same IP prefix to be summarized into one route. If a link connected to a device within an IP address range that has been summarized alternates between Up and Down, the link status change is not advertised to the devices beyond the IP address range. This prevents route flapping and improves network stability.

The abr-summary command configures route summarization on an ABR. When an ABR transmits routing information to other areas, it originates Type 3 Link Status Advertisements (LSAs) per network segment. If contiguous segments exist in this area, run the abr-summary command to summarize these segments into one segment so that the ABR sends only one summary LSA. The summarization reduces the routing table size and improves performance of the device.

Prerequisites

The segments that need to be summarized have been specified using the network command.

Precautions

This command applies only to ABRs. To configure route summarization on an AS boundary router (ASBR), run the asbr-summary command.
Route summarization cannot be configured for different areas in the same process.

Example

# In OSPF area 1, summarize routes in the network segments (10.42.10.0/24 and 10.42.110.0/24) into one 10.42.0.0/16, and advertise the summary route to other areas.

<HUAWEI> system-view
[~HUAWEI] ospf 100
[*HUAWEI-ospf-100] area 1
[*HUAWEI-ospf-100-area-0.0.0.1] network 10.42.10.0 0.0.0.255
[*HUAWEI-ospf-100-area-0.0.0.1] network 10.42.110.0 0.0.0.255
[*HUAWEI-ospf-100-area-0.0.0.1] abr-summary 10.42.0.0 255.255.0.0