Enabling or Disabling the Transmission of ICMP Unreachable Messages for Static Routes on Null Interfaces
You can configure a static route using the ip route command and direct traffic to the null interface by specifying the null 0 keyword with this command, instead of a next-hop or destination address.
To configure an IP static route with a null 0 interface as the next-hop:
- Issue the ip route command
with the null 0 keyword in Global Configuration
mode.host1(config)#ip route 192.168.10.0/24 null0
The default behavior for packets reaching null 0 interfaces with static routes takes effect, which is to discard the received packets and not send ICMP unreachable messages to the originator.
To enable the transmission of ICMP unreachable messages for IPv4 packets that reach the static route configured on the null 0 interface and are discarded:
- Issue the ip route command
with the null 0 and reject keywords in Global Configuration mode.host1(config)#ip route 192.168.10.0/24 null0 reject
To disable the transmission of ICMP unreachable messages for IPv4 packets that reach the static route configured on the null 0 interface and are discarded:
- Issue the ip route command
with the null 0 and discard keywords in Global Configuration mode.host1(config)#ip route 192.168.10.0/24 null0 discard
Use the no version to remove a static route from the routing table.
