BigIron RX Series Configuration Guide 19553-1001986-01Configuring forwarding parameters 7• Destination Unreachable messages – If the device receives an IP packet that it cannot deliverto its destination, the device discards the packet and sends a message back to the device thatsent the packet. The message informs the device that the destination cannot be reached bythe device.Disabling replies to broadcast ping requestsBy default, the device is enabled to respond to broadcast ICMP echo packets, which are pingrequests.To disable response to broadcast ICMP echo packets (ping requests), enter the following command.BigIron RX(config)# no ip icmp echo broadcast-requestSyntax: [no] ip icmp echo broadcast-requestIf you need to re-enable response to ping requests, enter the following command.BigIron RX(config)# ip icmp echo broadcast-requestDisabling ICMP destination unreachable messagesBy default, when the device receives an IP packet that the device cannot deliver, the device sendsan ICMP Unreachable message back to the host that sent the packet. You can selectively disable adevice’s response to the following types of ICMP Unreachable messages:• Administration – The packet was dropped by the Brocade device due to a filter or ACLconfigured on the device.• Fragmentation-needed – The packet has the Don’t Fragment bit set in the IP Flag field, but thedevice cannot forward the packet without fragmenting it.• Host – The destination network or subnet of the packet is directly connected to the device, butthe host specified in the destination IP address of the packet is not on the network.• Network – The device cannot reach the network specified in the destination IP address of thepacket.• Port – The destination host does not have the destination TCP or UDP port specified in thepacket. In this case, the host sends the ICMP Port Unreachable message to the device, whichin turn sends the message to the host that sent the packet.• Protocol – The TCP or UDP protocol on the destination host is not running. This message isdifferent from the Port Unreachable message, which indicates that the protocol is running onthe host but the requested protocol port is unavailable.• Source-route-failure – The device received a source-routed packet but cannot locate thenext-hop IP address indicated in the packet’s Source-Route option.You can disable the device from sending these types of ICMP messages on an individual basis.NOTEDisabling an ICMP unreachable message type does not change the device’s ability to forwardpackets. Disabling ICMP unreachable messages prevents the device from generating or forwardingthe unreachable messages.To disable all ICMP Unreachable messages, enter the following command.BigIron RX(config)# no ip icmp unreachable
