H3C Technologies H3C SecPath F1000-E - Manual (Page 426)

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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.
• Configure 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.
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 ]
Not configured by default.
The command is available on
an ABR only.
• Configure 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:
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 } [ tag tag |
not-advertise | cost cost ] * The command is available on
an ASBR only.
Not configured by default.
• Configure OSPF inbound route filtering.
NOTE:
For more information about IP prefix list and routing policy, see "Configuring routing policies."
OSPF calculates routes by using LSAs. The calculated routes can be filtered and only permitted
routes are installed into the OSPF routing table.
OSPF provides the following filtering methods: filters routing information by destination address
through ACLs and IP address prefixes; filters routing information by next hop through the filtering