708 BigIron RX Series Configuration Guide53-1002253-01Configuring OSPF25Configure external route summarizationWhen the BigIron RX is an OSPF Autonomous System Boundary Router (ASBR), you can configure itto advertise one external route as an aggregate for all redistributed routes that are covered by aspecified address range.When you configure an address range, the range takes effect immediately. All the imported routesare summarized according to the configured address range. Imported routes that have alreadybeen advertised and that fall within the range are flushed out of the AS and a single routecorresponding to the range is advertised.If a route that falls within a configured address range is imported by the device, no action is taken ifthe device has already advertised the aggregate route; otherwise the device advertises theaggregate route. If an imported route that falls with in a configured address range is removed bythe device, no action is taken if there are other imported routes that fall with in the same addressrange; otherwise the aggregate route is flushed.You can configure up to 32 address ranges. The device sets the forwarding address of theaggregate route to zero and sets the tag to zero.If you delete an address range, the advertised aggregate route is flushed and all imported routesthat fall within the range are advertised individually.If an external LSDB overflow condition occurs, all aggregate routes are flushed out of the AS, alongwith other external routes. When the device exits the external LSDB overflow condition, all theimported routes are summarized according to the configured address ranges.NOTEIf you use redistribution filters in addition to address ranges, the BigIron RX applies the redistributionfilters to routes first, then applies them to the address ranges.NOTEIf you disable redistribution, all the aggregate routes are flushed, along with other imported routes.NOTEThis option affects only imported, type 5 external routes. A single type 5 LSA is generated andflooded throughout the AS for multiple external routes. Type 7-route redistribution is not affected bythis feature. All type 7 routes will be imported (if redistribution is enabled). To summarize type 7 LSAsor exported routes, use NSSA address range summarization.To configure a summary address for OSPF routes, enter commands such as the following.BigIron RX(config-ospf-router)# summary-address 10.1.0.0 255.255.0.0The command in this example configures summary address 10.1.0.0, which includes addresses10.1.1.0, 10.1.2.0, 10.1.3.0, and so on. For all of these networks, only the address 10.1.0.0 isadvertised in external LSAs.Syntax: summary-address The parameter specifies the network address.The parameter specifies the network mask.To display the configured summary addresses, enter the following command at any level of the CLI.BigIron RX(config-ospf-router)# show ip ospf configOSPF Redistribution Address Ranges currently defined:
