Brocade TurboIron 24X Series Configuration Guide - Manual (Page 671)

Brocade TurboIron 24X Series Configuration Guide 637
53-1003053-01
Configuring OSPF
The router software can use the route information it learns through OSPF to determine the paths
and costs. Example OSPF network with four equal-cost paths
In the example in Figure , the switch has four paths to R1:
• Device->R3
• Device->R4
• Device->R5
• Device->R6
Normally, the switch will choose the path to the R1 with the lower metric. For example, if R3 metric
is 1400 and R4 metric is 600, the switch 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 switch now has four equal-cost paths to R1. To allow the switch 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 – 6 paths.
NOTE
The switch is not source routing in these examples. The switch 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 474.
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.
OSPF Area 0
H1
H2
H3
H4
R1
R3
R4
R5
R6
Device