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K-31
User Guide for Cisco Security Manager 3.2
OL-16066-01
Appendix K Router Platform User Interface Reference
Advanced Interface Settings Page
ICMP Messages settings
Enable Redirect
Messages
When selected, enables the sending of Internet Control Message Protocol
(ICMP) redirect messages if the device is forced to resend a packet through
the same interface on which it was received to another device on the same
subnet. This is the default.
When deselected, disabled redirect messages.
Redirect messages are sent when the device wants to instruct the originator
of the packet to remove it from the route and substitute a different device that
offers a more direct path to the destination.
Enable Unreachable
Messages
When selected, enables the sending of ICMP unreachable messages. This is
the default.
When deselected, disables unreachable messages.
Unreachable messages are sent in two circumstances:
• If the interface receives a nonbroadcast packet destined for itself that
uses an unknown protocol. In this case, it sends an ICMP unreachable
message to the source.
• If the device receives a packet that it cannot deliver to its ultimate
destination because it knows of no route to the destination address. In
this case, it sends an ICMP host unreachable message to the originator
of the packet.
Note This is the only advanced setting supported by the null0 interface.
Enable Mask Reply
Messages
When selected, enables the sending of ICMP mask reply messages.
When deselected, disables mask reply messages. This is the default.
Mask reply messages are sent in response to mask request messages, which
are sent when a device needs to know the subnet mask for a particular
subnetwork.
Table K-13 Advanced Interface Settings Dialog Box (Continued)