By default, the device does not respond to ICMP unreachable notifications.
Interface configuration mode
Use the no form of the command to disable the feature.
The following example enables a device to respond to ICMP unreachable notifications to the indicated source.
device# configure terminal device(config)# interface ve 2 device(config-int-ve-2)# ip address 2.1.1.1/24 device(config-int-ve-2)# ip icmp unreachable