Riverstone Networks WICT1-12 - Manual (Page 220)

14-4 Riverstone Networks RS Switch Router User Guide Release 8.0
Configuring OSPF Areas OSPF Configuration Guide
14.5.1 Configuring Summary Ranges
To reduce the amount of routing information propagated between areas, you can configure summary-ranges on Area
Border Routers (ABRs). On the RS, summary-ranges are created using the
ospf add summary-range
command –
the networks specified using this command describe the scope of an area. Intra-area Link State Advertisements (LSAs)
that fall within the specified ranges are not advertised into other areas as inter-area routes. Instead, the specified ranges
are advertised as summary network LSAs.
14.5.2 Configuring Stub Areas
Information about routes which are external to the OSPF routing domain is not sent into a stub area. Instead, if the
stub-cost
parameter is specified, the ABR generates a default external route into the stub area for destinations
outside the OSPF routing domain. The
stub-cost
specifies the cost to be used to inject a default route into a stub
area. If this parameter is not specified, no default route is injected into the OSPF stub area.
To define an OSPF stub area, enter the following command in Configure mode.
The RS provides two ways to reduce the number of summary link advertisements (LSA Type 3) sent into a stub area.
To prevent the router from sending any Type 3 LSAs into the stub area, specify the
no-summary
keyword with the
ospf set area
command. This makes the stub area a totally stub area with no Type 3 LSAs going through the stub.
Alternatively, you can configure summary filters to filter out specific summary LSAs from the stub area. Use this
command for Type 3 LSA you want to block. Type 3 LSAs that are not specified in this command will be sent into the
stub area.
To filter specific summary LSAs from a stub area, enter the following command in Configure mode:
Add a network to an OSPF area for
summarization.
ospf add network|summary-range
<IPaddr-mask>
to-area
<area-addr>
|
backbone [restrict] [host-net]
Specify an OSPF area to be a stub area.
ospf set area
<area-num>
stub
[no-summary][stub-cost
<num>
]
Configure summary filters.
ospf add summary-filters to area
<area-ID>
|backbone[filter
<number-or-string>
][network
<IPaddr-mask>
]|all|default|exact|refines|
between
<number>
|host-net