Destination unreachable messages
If the routing switch receives an IP packet that it cannot deliver to its destination, the routing switch discards
the packet and sends a message back to the device that sent the packet to the routing switch. The message
informs the device that the destination cannot be reached by the routing switch.
Address mask replies
You can enable or disable ICMP address mask replies.
Disabling ICMP destination unreachable messages
By default, when a device receives an IP packet that the device cannot deliver, the device sends an ICMP
unreachable message back to the host that sent the packet. The following types of ICMP unreachable messages
are generated:
Administration
The packet was dropped by the device due to a filter or ACL configured on the device.
Fragmentation-needed
The packet has the "Don't Fragment" bit set in the IP Flag field, but the device cannot forward the packet
without fragmenting it.
Host
The destination network or subnet of the packet is directly connected to the device, but the 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 the packet.
Port
The destination host does not have the destination TCP or UDP port specified in the packet. In this case, the
host sends the ICMP Port Unreachable message to the device, which in 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 is different from the Port
Unreachable message, which indicates that the protocol is running on the host but the requested protocol port
is unavailable.
Source-route-failure
The device received a source-routed packet but cannot locate the next-hop IP address indicated in the
packet's Source-Route option.
NOTE:
Disabling an ICMP Unreachable message type does not change the device's ability to
forward packets. Disabling ICMP Unreachable messages prevents the device from generating or
forwarding the Unreachable messages.
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Aruba 3810 / 5400R Multicast and Routing Guide for ArubaOS-
Switch 16.08