3Com Switch 8807, Configuration Manual

Page: 319 / 883

Configuring OSPF 319
Configuring the Route
Summary of OSPF
Configuring the route summary of OSPF area
Route summary means that ABR can aggregate information of the routes of the
same prefix and advertise only one route to other areas. An area can be
configured with multiple aggregate segments, thereby OSPF can summarize them.
When the ABR transmits routing information to other areas, it will generate
Sum_net_Lsa (type-3 LSA) per network. If some continuous networks exist in this
area, you can use the
abr-summary command to summarize these segments into
one segment. Thus, the ABR only needs to send an aggregated LSA, and all the
LSAs in the range of the aggregate segment specified by the command will not be
transmitted separately. This can reduce the LSDB size in other areas.
Once the aggregated segment of a certain network is added to the area, all the
internal routes of the IP addresses in the range of the aggregated segment will no
longer be separately advertised to other areas. Only the route summary of the
whole aggregated network will be advertised. But if the range of the segment is
restricted by the keyword
not-advertise , the route summary of this segment will
not be advertised. This segment is represented by IP address and mask.
Route summary can take effect only when it is configured on ABRs.
Perform the following configuration in OSPF area view.
By default, route summary is disabled on ABRs.
Configuring summarization of imported routes by OSPF
OSPF of the Switch 8800 Family series supports route summary of imported
routes.
Perform the following configurations in OSPF view.
By default, summarization of imported routes is disabled.
After the summarization of imported routes is configured, if the local router is an
autonomous system border router (ASBR), this command summarizes the
imported Type-5 LSAs in the summary address range. When NSSA is configured,
this command will also summarize the imported Type-7 LSA in the summary
address range.
Table 283 Configure the route summary of OSPF area
Operation Command
Configure route summary of OSPF area
abr-summary ip - address mask [ advertise |
not-advertise ]
Cancel route summary of OSPF area undo abr-summary ip - address mask
Table 284 Configure summarization of imported routes by OSPF
Operation Command
Configure summarization of imported routes
by OSPF asbr-summary ip - address mask [
not-advertise | tag value ]
Remove summarization of routes imported
into OSPF
undo asbr-summary ip - address mask