Brocade Communications Systems FastIron SX 1600, Configuration Manual, Page: 66 / 593

Configuring a "Null" route
You can configure the Layer 3 switch to drop IP packets to a specific network or host address by configuring a "null" (sometimes called
"null0") static route for the address. When the Layer 3 switch receives a packet destined for the address, the Layer 3 switch drops the
packet instead of forwarding it.
To configure a null static route, use the following CLI method.
To configure a null static route to drop packets destined for network 10.157.22.x, enter the following commands.
device(config)# ip route 10.157.22.0 255.255.255.0 null0
device(config)# write memory
Syntax: ip route ip-addr ip-mask null0 [ metric ] [ distance num ]
or
Syntax: ip route ip-addr / mask-bits null0 [ metric ] [ distance num ]
To display the maximum value for your device, enter the show default values command. The maximum number of static IP routes the
system can hold is listed in the ip-static-route row in the System Parameters section of the display. To change the maximum value, use
the
system-max ip-static-route command at the global CONFIG level.
The ip-addr variable specifies the network or host address. The Layer 3 switch will drop packets that contain this address in the
destination field instead of forwarding them.
The ip-mask variable specifies the network mask. Ones are significant bits and zeros allow any value. For example, the mask
255.255.255.0 matches on all hosts within the Class C subnet address specified by ip-addr . Alternatively, you can specify the number
of bits in the network mask. For example, you can enter 10.157.22.0/24 instead of 10.157.22.0 255.255.255.0.
The null0 variable indicates that this is a null route. You must specify this parameter to make this a null route.
The metric variable adds a cost to the route. You can specify from 1 through 16. The default is 1.
The distance num variable configures the administrative distance for the route. You can specify a value from 1 through 255. The default
is 1. The value 255 makes the route unusable.
NOTE
The last two variables 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.
Naming a static IP route
You can assign a name to a static IP route. A static IP route name serves as a description of the route. The name can be used to more
readily reference or identify the associated static route.
NOTE
The static route name is an optional feature. It does not affect the selection of static
routes.
The Brocade device does not check for the uniqueness of names assigned to static routes. Static routes that have the same or different
next hops can have the same or different names. Due to this, the same name can be assigned to multiple static routes to group them.
The name is then used to reference or identify a group of static routes.
The option to assign a name to a static route is displayed after you select either an outgoing interface type or configure the next hop
address.
To assign a name to a static route, enter commands such as the following.
device(config)# ip route 10.22.22.22 255.255.255.255 eth 1/1/1 name abc
Configuring IP parameters - Layer 3 switches
FastIron Ethernet Switch Layer 3 Routing
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