Configuring A "Null" Route - HP ProCurve Series 4100GL Management And Configuration Manual

IP Routing Features
Configuring Static IP Routes

Configuring a "Null" Route

You can configure the routing 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 routing switch receives a packet destined for the
address, the routing switch drops the packet instead of forwarding it.
To configure a null static route to drop packets destined for network
209.157.22.x, enter the following commands:
HPswitch(config)# ip route 209.157.22.0 255.255.255.0 reject
HPswitch(config)# write memory
Syntax: ip route < ip-addr > < ip-mask > reject
— or —
ip route < ip-addr >/< mask-bits > reject
Using this command, the routing switch will drop packets that contain the
specified IP address in the destination field instead of forwarding them.
The reject parameter indicates that this is a null route. You must specify this
parameter to make this a null route.
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