Brocade Virtual ADX Switch and Router Guide (Supporting ADX v03.1.00) - Manual (Page 144)

130 Brocade Virtual ADX Switch and Router Guide
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Configuring OSPF
6
NOTE
The Brocade router is not source routing in these examples. The router is concerned only with the
paths to the next-hop routers, not the entire paths to the destination hosts.
OSPF load sharing is enabled by default when IP load sharing is enabled. To configure IP load
sharing parameters, refer to
“Configuring IP load sharing” on page 77.
Configure external route summarization
When the Layer 3 Switch is an OSPF Autonomous System Boundary Router (ASBR), you can
configure it to advertise one external route as an aggregate for all redistributed routes that are
covered by a specified address range.
When you configure an address range, the range takes effect immediately. All the imported routes
are summarized according to the configured address range. Imported routes that have already
been advertised and that fall within the range are flushed out of the AS and a single route
corresponding to the range is advertised.
If a route that falls within a configured address range is imported by the Layer 3 Switch, no action is
taken if the Layer 3 Switch has already advertised the aggregate route; otherwise the Layer 3
Switch advertises the aggregate route. If an imported route that falls with in a configured address
range is removed by the Layer 3 Switch, no action is taken if there are other imported route(s) that
fall with in the same address range; otherwise the aggregate route is flushed.
You can configure up to 32 address ranges. The Layer 3 Switch 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 flushed and all imported routes
that fall within the range are advertised individually.
If an external LSDB overflow condition occurs, all aggregate routes are flushed out of the AS, along
with other external routes. When the Layer 3 Switch exits the external LSDB overflow condition, all
the imported routes are summarized according to the configured address ranges.
NOTE
If you use redistribution filters in addition to address ranges, the Layer 3 Switch applies the
redistribution filters to routes first, then applies them to the address ranges.
NOTE
If you disable redistribution, all the aggregate routes are flushed, along with other imported routes.
NOTE
This option affects only imported, type 5 external routes. A single type 5 LSA is generated and
flooded throughout the AS for multiple external routes. Type 7-route redistribution is not affected 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 configure a summary address for OSPF routes, enter commands such as the following.
Virtual ADX(config-ospf-router)# summary-address 10.1.0.0 255.255.0.0
The command in this example configures 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.