Congure external route summarization
When the device is an OSPF Autonomous System Boundary Router (ASBR), you can congure it to advertise one external route as an
aggregate for all redistributed routes that are covered by a specied address range.
When you congure an address range, the range takes eect immediately. All the imported routes are summarized according to the
congured address range. Imported routes that have already been advertised and that fall within the range are ushed out of the AS and
a single route corresponding to the range is advertised.
If a route that falls within a congured address range is imported by the device, no action is taken if the device has already advertised the
aggregate route; otherwise the device advertises the aggregate route. If an imported route that falls with in a congured address range is
removed by the device, no action is taken if there are other imported routes that fall with in the same address range; otherwise the
aggregate route is ushed.
You can congure up to 32 address ranges. The device sets the forwarding address of the aggregate route to zero and sets the tag to
zero.
If you delete an address range, the advertised aggregate route is ushed and all imported routes that fall within the range are advertised
individually.
If an external LSDB overow condition occurs, all aggregate routes are ushed out of the AS, along with other external routes. When the
device exits the external LSDB overow condition, all the imported routes are summarized according to the congured address ranges.
NOTE
If you use redistribution lters in addition to address ranges, the device applies the redistribution lters to routes rst, then
applies them to the address ranges.
NOTE
If you disable redistribution, all the aggregate routes are ushed, along with other imported
routes.
NOTE
This option aects only imported, type 5 external routes. A single type 5 LSA is generated and ooded throughout the AS for
multiple external routes. Type 7-route redistribution is not aected by this feature. All type 7 routes will be imported (if
redistribution is enabled). To summarize type 7 LSAs or exported routes, use NSSA address range summarization.
To congure a summary address for OSPF routes, enter commands such as the following.
device(config-ospf-router)# summary-address 10.1.0.0 255.255.0.0
The command in this example
congures summary address 10.1.0.0, which includes addresses 10.1.1.0, 10.1.2.0, 10.1.3.0, and so
on. For all of these networks, only the address 10.1.0.0 is advertised in external LSAs.
Syntax: summary-address ip-addr ip-mask
The ip-addr parameter species the network address.
The ip-mask parameter species the network mask.
To display the congured summary addresses, enter the following command at any level of the CLI.
device# show ip ospf config
Router OSPF: Enabled
Nonstop Routing: Disabled
Graceful Restart: Disabled
Graceful Restart Helper: Enabled
Graceful Restart Time: 120
Graceful Restart Notify Time: 0
Redistribution: Disabled
Conguring OSPF
FastIron Ethernet Switch Layer 3 Routing
53-1003627-04 253
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