Brocade BigIron RX Series Configuration Guide - Manual (Page 860)

782 BigIron RX Series Configuration Guide
53-1002484-04
Configuring OSPF
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• BigIron RX ->R6
Normally, the BigIron RX will choose the path to the R1 with the lower metric. For example, if R3’s
metric is 1400 and R4’s metric is 600, the BigIron RX will always choose R4.
However, suppose the metric is the same for all four routers in this example. If the costs are the
same, the router now has four equal-cost paths to R1. To allow the router to load share among the
equal cost routes, enable IP load sharing. The software supports four equal-cost OSPF paths by
default when you enable load sharing. You can specify from 2 – 8 paths.
NOTE
The BigIron RX 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 211.
Configure external route summarization
When the BigIron RX 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 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 configured 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 flushed.
You can configure 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 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 device 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 BigIron RX 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.