R3303-HP HSR6800 Routers Layer 3 - IP Routing Configuration Guide
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• Configure filters if routing information filtering is needed.
Configuring OSPF route summarization
You can configure route summarization on an ABR or ASBR to summarize routes with the same prefix into
a single route and distribute it to other areas.
Route summarization reduces the routing information exchanged between areas and the sizes of routing
tables, improving router performance.
Configuring route summarization on an ABR
If contiguous network segments are available in the area, you can summarize them into a single network
segment. An ABR generates Type-3 LSAs on a per network segment basis for an attached non-backbone
area. In this way, the ABR in the area distributes only the summary LSA to reduce the scale of LSDBs on
routers in other areas and the influence of topology changes.
For example, in an area are three internal routes 19.1.1.0/24, 19.1.2.0/24, and 19.1.3.0/24. By
configuring route summarization on the ABR, the three routes are summarized into the route 19.1.0.0/16
that is advertised to other areas.
To configure route summarization on an ABR:
Ste
p
Command
Remarks
1. Enter system view.
system-view N/A
2. Enter OSPF view.
ospf [ process-id | router-id router-id
| vpn-instance vpn-instance-name ] *
N/A
3. Enter OSPF area view.
area area-id N/A
4. Configure ABR route
summarization.
abr-summary ip-address { mask |
mask-length } [ advertise |
not-advertise ] [ cost cost ]
Not configured by default.
The command is available on an
ABR only.
Configuring route summarization when redistributing routes into OSPF on an ASBR
Without route summarization, an ASBR advertises each redistributed route in a separate ASE LSA. After
a summary route is configured, the ASBR advertises only the summary route in an ASE LSA instead of
more specific routes, reducing the number of LSAs in the LSDB.
The ASBR summarizes redistributed Type-5 LSAs that fall into the specified address range. If the ASBR is
in an NSSA area, it also summarizes Type-7 LSAs that fall into the specified address range. If the ASBR
is also the ABR, it summarizes Type-5 LSAs translated from Type-7 LSAs.
To configure route summarization when redistributing routes into OSPF on an ASBR:
Ste
p
Command
Remarks
1. Enter system view.
system-view N/A
2. Enter OSPF view.
ospf [ process-id | router-id router-id
| vpn-instance vpn-instance-name ]*
N/A
3. Configure ASBR route
summarization.
asbr-summary ip-address { mask |
mask-length } [ tag tag | not-advertise
| cost cost ] *
The command is available on an
ASBR only.
Not configured by default.