The abr-summary command configures route summarization on Area Border Routers (ABRs).
The undo abr-summary command disables route summarization on ABRs.
By default, route summarization is not configured on ABRs.
abr-summary ip-address mask [ cost { cost | inherit-minimum } | [ advertise [ generate-null0-route ] | not-advertise | generate-null0-route [ advertise ] ] ] *
undo abr-summary ip-address mask
| Parameter | Description | Value |
|---|---|---|
ip-address |
Specifies the IP address of a summarized route. |
The value is in dotted decimal notation. |
mask |
Specifies the mask of the IP address of the summarized route. |
The value is in dotted decimal notation. |
advertise |
Specifies to advertise the summarized route. By default, the summarized route is advertised. |
- |
generate-null0-route |
Specifies to generate a black-hole route in the RM module, which is used to prevent routing loops. |
- |
cost cost |
Specifies the cost of the summarized route. |
The value is an integer ranging from 0 to 16777214. By default, the cost of the summarized route is the highest cost among the cost of the routes being summarized. |
inherit-minimum |
Indicates that the smallest cost of the specific routes before the summarization is used as the cost of the summarized route. This parameter can be run only in the private OSPF processes. |
- |
not-advertise |
Specifies not to advertise the summarized route. By default, the summarized route is advertised. |
- |
Usage Scenario
On a large-scale OSPF network, route searching speed may decrease because of the large size of the routing table. You can configure route summarization to reduce the size of the routing table and simplify management.
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 not within the IP address range. This prevents route flapping and improves network stability.
The abr-summary command configures route summarization on ABRs. When an ABR transmits routing information to other areas, it originates Type-3 LSAs per network segment. If any consecutive segments exist in this area, you can run the abr-summary command to summarize these segments into one segment. An ABR sends only one summarized LSA. Any LSA that belongs to the summarized network segment specified by the command is not transmitted separately. Therefore, the size of the routing table is reduced, and router performance is improved.
Prerequisites
The network command has been run to specify the segments that need to be summarized before configuring route summarization.
Precautions
This command is applicable only to ABRs for route summarization in an area. The asbr-summary command configures AS Boundary Routers (ASBRs) to summarize routes imported by OSPF.
ABR routes cannot configure route summarization for different areas in the same process.
# In OSPF area 1, summarize routes in the two network segments, 10.1.10.0/32 and 10.1.110.0/32, into one summarized route 10.1.0.0, and advertise the summarized route to other areas.
<sysname> system-view [sysname] ospf 100 [sysname-ospf-100] area 1 [sysname-ospf-100-area-0.0.0.1] network 10.1.10.0 0.0.0.0 [sysname-ospf-100-area-0.0.0.1] network 10.1.110.0 0.0.0.0 [sysname-ospf-100-area-0.0.0.1] abr-summary 10.1.0.0 255.255.0.0