Dell BigIron RX Series, Руководство по настройке

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204 BigIron RX Series Configuration Guide
53-1002253-01
Configuring forwarding parameters
7
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IP load sharing – If you configure more than one static route to the same destination, and the
routes have different next-hop gateways but have the same metrics, the device load balances
among the routes using basic round-robin. For example, if you configure two static routes with
the same metrics but to different gateways, the device alternates between the two routes. For
information about IP load balancing, refer to
“Configuring IP load sharing” on page 209.
•
Backup Routes – If you configure multiple static IP routes to the same destination, but give the
routes different next-hop gateways and different metrics, the device will always use the route
with the lowest metric. If this route becomes unavailable, the device will fail over to the static
route with the next-lowest metric, and so on.
NOTE
You also can bias the device to select one of the routes by configuring them with different
administrative distances. However, make sure you do not give a static route a higher administrative
distance than other types of routes, unless you want those other types to be preferred over the static
route. For a list of the default administrative distances, refer to
“Changing administrative distances”
on page 767.
The steps for configuring the static routes are the same as described in the previous section. The
following sections provide examples.
To configure multiple static IP routes, enter commands such as the following.
BigIron RX(config)# ip route 192.128.2.69 255.255.255.0 209.157.22.1
BigIron RX(config)# ip route 192.128.2.69 255.255.255.0 192.111.10.1
The commands in the example above configure two static IP routes. The routes go to different
next-hop gateways but have the same metrics. These commands use the default metric value (1),
so the metric is not specified. These static routes are used for load sharing among the next-hop
gateways.
The following commands configure static IP routes to the same destination, but with different
metrics. The route with the lowest metric is used by default. The other routes are backups in case
the first route becomes unavailable. The device uses the route with the lowest metric if the route is
available.
BigIron RX(config)# ip route 192.128.2.69 255.255.255.0 209.157.22.1
BigIron RX(config)# ip route 192.128.2.69 255.255.255.0 192.111.10.1 2
BigIron RX(config)# ip route 192.128.2.69 255.255.255.0 201.1.1.1 3
In this example, each static route has a different metric. The metric is not specified for the first
route, so the default (1) is used. A metric is specified for the second and third static IP routes. The
second route has a metric of two and the third route has a metric of 3. Thus, the second route is
used only of the first route (which has a metric of 1) becomes unavailable. Likewise, the third route
is used only if the first and second routes (which have lower metrics) are both unavailable.
For complete syntax information, refer to “Configuring a static IP route” on page 201.
Configuring standard static IP routes and interface or null static
routes to the same destination
You can configure a null0 or interface-based static route to a destination and also configure a
normal static route to the same destination, so long as the route metrics are different.