Brocade Multi-Service IronWare Switching Configuration Guide (Supporting R05.6.00) - Manual (Page 821)

Multi-Service IronWare Switching Configuration Guide 791
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Configuring static routes
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NOTE
The last three 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.
Dropping traffic sent to the null0 interface In hardware
Traffic sent to the null0 interface is done in hardware; that is, by programming the CAM to discard
traffic sent to the null0 interface. This improves forwarding efficiency and reduces the burden on
the Brocade device’s CPU.
Hardware dropping for IP traffic sent to the null0 interface is supported.
You can optionally configure the Brocade device to drop traffic sent to the default IP route address
in hardware. To do this, enter the following commands.
Brocade(config)# ip route 0.0.0.0 0.0.0.0 null0
Brocade(config)# ip hw-drop-on-def-route
Syntax: [no] ip hw-drop-on-def-route
CAM default route aggregation
Configuring the Brocade device to drop traffic sent to the default IP route address in hardware
causes the device to program 32-bit host CAM entries for each destination address using the
default route, which could consume the CAM space. To prevent this from happening, you can
enable the CAM Default Route Aggregation feature. To do this, enter the following command.
Brocade(config)# ip dr-aggregate
Syntax: [no] ip dr-aggregate
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 Brocade 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 Brocade device alternates between
the two routes. For information about IP load balancing, refer to
“Configuring IP load sharing”
on page 804.
• 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 Brocade device will always use
the route with the lowest metric. If this route becomes unavailable, the Brocade device will fail
over to the static route with the next-lowest metric, and so on.
NOTE
You also can bias the Brocade 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.