Brocade Virtual ADX Switch and Router Guide (Supporting ADX v03.1.00) User Manual
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Brocade Virtual ADX Switch and Router Guide
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Configuring IP parameters
4
NOTE
The last two parameters are optional and do not affect the null route, unless you configure the
administrative distance to be 255. In this case, the route is not used and the traffic might be
forwarded instead of dropped.
Configuring load balancing and redundancy using multiple static routes to the
same destination
You can configure multiple static IP routes to the same destination, for the following benefits:
•
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 Virtual ADX 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 Virtual ADX alternates between the
two routes. For information about IP load balancing, refer to
•
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 Virtual ADX will always use the
route with the lowest metric. If this route becomes unavailable, the Virtual ADX will fail over to
the static route with the next-lowest metric, and so on.
NOTE
You also can bias the Virtual ADX 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.
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.
Virtual ADX(config)# ip route 10.128.2.69 255.255.255.0 10.157.22.1
Virtual ADX(config)# ip route 10.128.2.69 255.255.255.0 10.111.10.1
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 Virtual ADX uses the route with the lowest metric if the
route is available.
Virtual ADX(config)# ip route 10.128.2.69 255.255.255.0 10.157.22.1
Virtual ADX(config)# ip route 10.128.2.69 255.255.255.0 10.111.10.1 2
Virtual ADX(config)# ip route 10.128.2.69 255.255.255.0 10.1.1.1 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.