3Com S7902E, Руководство по настройке

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Configuring OSPF Route Summarization
Route summarization: An ABR or ASBR summarizes routes with the same prefix into a single route and
distribute it to other areas.
Through route summarization, routing information across areas and the size of routing tables on routers
will be reduced, improving calculation speed of routers.
Assume 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 into other areas.
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 topological changes.
Follow these steps to configure route summarization on an ABR:
To do… Use the command… Remarks
Enter system view system-view
—
Enter OSPF view
ospf [ process-id | router-id
router-id | vpn-instance
instance-name ] *
—
Enter OSPF area view area area-id
—
Configure ABR route
summarization
abr-summary ip-address { mask
| mask-length } [ advertise |
not-advertise ] [ cost cost ]
Required
The command is available on
an ABR only.
Not configured by default.
Configuring route summarization when redistributing routes into OSPF on an ASBR
If summarization for redistributed routes is not configured on an ASBR, it will advertise each
redistributed route in a separate ASE LSA. After a summary is configured on the ASBR, it advertises
only the summary route in an ASE LSA instead of more specific routes, thus reducing the number of
LSAs in the LSDBs.
If summarization for redistributed routes is configured on an ASBR, it will summarize 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 will
summarize Type-5 LSAs translated from Type-7 LSAs.
Follow these steps to configure route summarization when redistributing routes into OSPF on an ASBR:
To do… Use the command… Remarks
Enter system view system-view
—