73
•
Enable OSPF.
•
Configure filters if routing information filtering is needed.
Configuring OSPF route summarization
Configure route summarization on an ABR or ASBR to summarize contiguous networks into a single
network and distribute it to other areas.
Route summarization reduces the routing information exchanged between areas and the size of routing
tables, and improves routing performance. For example, three internal networks 19.1.1.0/24,
19.1.2.0/24, and 19.1.3.0/24 are available within an area. You can summarize the three networks into
network 19.1.0.0/16, and advertise the summary network to other areas.
Configuring route summarization on an ABR
After you configure a summary route on an ABR, the ABR generates a summary LSA instead of more
specific LSAs so that the scale of LSDBs on routers in other areas and the influence of topology changes
are reduced.
To configure route summarization on an ABR:
Step 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
]
By default, no route summarization
is configured.
The command takes effect only on
an ABR.
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
you configure a summary route, 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:
Step 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
} [
cost
cost
|
not-advertise
|
nssa-only
|
tag
tag
] *
By default, no ASBR route
summarization is configured.
The command takes effect only on an
ASBR.
