When OSPF is enabled and multiple, equal-cost, next-hop routes are available for traffic destinations on different
subnets, this feature, by default, enables load-sharing among up to four next-hop routes.
1 - 4 :
Specifies the maximum number of equal-cost next-hop paths the router allows.
Default: 4; range: 2–4
The
no
form of the command disables this load-sharing so that only one route in a group of multiple, equal-cost,
next-hop routes is used for traffic that could otherwise be load-shared across multiple routes.
For example, in
Figure 45: Example of load-sharing traffic to different subnets through equal-cost next-hop
on page 263, the next-hop routers "B", "C", and "D" are available for equal-cost load-sharing of eligible
traffic. Disabling IP load-sharing means that router "A" selects only one next-hop router for traffic that is actually
eligible for load-sharing through different next-hop routers.
Default: Enabled with four equal-cost, next-hop routes allowed.
NOTE:
This command enables or disables load-sharing for both IPv4 (OSPFv2) and IPv6 (OSPFv3)
operation. For more information, see the IPv6 configuration guide for your switch.
In the default configuration, IP load-sharing is enabled by default. However, it has no effect unless IP routing and
OSPF are enabled.
Viewing the current IP load-sharing configuration
Use the
show running
command to view the currently active IP load-sharing configuration, and
show config
to view the IP load-sharing configuration in the startup-config file. (While in its default configuration, IP load-
sharing does not appear in the command output.)
If IP load sharing is configured with non-default settings (disabled or configured for either two or three equal-cost
next-hop paths), the current settings are displayed in the command output.
Figure 38: Displaying a non-default IP load-sharing configuration
Overview of OSPF
OSPF is a link-state routing protocol applied to routers grouped into OSPF areas identified by the routing
configuration on each routing switch. The protocol uses LSAs transmitted by each router to update neighboring
routers regarding its interfaces and the routes available through those interfaces. Each routing switch in an area
also maintains a link-state database (LSDB) that describes the area topology. (All routers in a given OSPF area
have identical LSDBs.) The routing switches used to connect areas to each other flood summary link LSAs and
external link LSAs to neighboring OSPF areas to update them regarding available routes. Through this means,
each OSPF router determines the shortest path between itself and a desired destination router in the same OSPF
domain (AS.)Routed traffic in an OSPF AS is classified as one of the following:
Chapter 11 Open Shortest Path First Protocol (OSPF)
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